In the construction of plant, the extent of surface is quite as often required as cubic capacity, simple rules may here be useful. To find the surface of a globe or sphere, multiply the diameter by its circumference and the product will be its convex surface. To find the convex surface of any segment or zone of a sphere, multiply the circumference of the whole sphere by the height of the segment or zone, and the product will be the convex surface.

To find the weight of an iron sphere from its diameter, divide nine times the cube of the diameter (in inches) by 64, which will express the required weight in pounds. To determine the diameter of an iron sphere of known weight (such as for counterbalance weights, &c.) multiply the weight by 7112, then take the cube root of the product for the diameter.

Turning now to the measuring of liquids in motion, as distinguished from their measurement in a state of rest, we have, perhaps, one of the most important problems that the chemical engineer has to encounter. Unfortunately, though water can be measured with very fair accuracy by means of a "meter," yet most chemical liquids and meters do not agree in contact, either the meter is rusted, or else corroded, or furred up with the majority of liquids requiring to be measured. A steady and well regulated flow of liquid can, however, be maintained by means of an ordinary tap or valve connected with a cistern so arranged as to give a constant head, this may be done by means of a regulating valve and float shown in the accompanying illustration.

The main store-tank is connected with the regulating valve on the inlet side, so that the regulating tank is always full to a constant level; under these conditions, the outflow tap, when once regulated, will deliver a constant volume. Of course, the tank, valve, and float will have to be constructed of suitable materials. An application of the principle of Marriotte's bottle can be made in many operations, but the difficulty of replenishing the contents, puts it out of court in all but small experiments.

In some cases it is not so necessary to have a constant or well regulated supply, as to know what volume is passing at the moment. A flow of this kind can best be measured by its passage through a carefully prepared orifice, and as this method is likely to be of great use in many operations, I will give the details of construction of an appliance to measure from 400 gallons to 1,400 gallons per hour.

A cast iron open top box of half-inch metal should be constructed as shown in the figures 2 and 3, about 20 inches deep and 15 inches wide, the midfeather runs to within an an inch of the bottom and forms two chambers, one 6 inches and the other 12 inches long. The liquid it is desired to measure is admitted into the larger chamber of the two, marked "inlet chamber."

The liquid flows underneath the midfeather into the outlet chamber, where it finds an exit at the orifice specially provided. For this purpose, an aperture, 21⁄2 inches square, is cast in the box, in front of which is fixed a brass plate (fig. 4) pierced with a carefully regulated aperture, and filed away to form knife edges. An orifice of one inch square will serve for measuring quantities varying from 400 to 900 gallons per hour, while an orifice 14 x 11⁄2 inches, is suitable for volumes from 800 gallons to 1,400 gallons per hour. A glass water-gauge stands outside the box as shown, behind

THE
HE following circular was published in the Times of August 6:-

"TO DISTILLERS AND THE WHOLESALE WINE TRADE. "From Messrs. Delvendahl and Kuentzel, Berlin and Malmo, essences, essential oils, colours, &c, manufacturers, and distillers. "21, Ritterstrasse, Berlin, S., July, 1890. "Dear Sirs,-We take leave to draw your attention to some of our specialities concerning your trade and should consider it a great favour if you will give same a trial when an opportunity offers.

"We manufacture :

"1. Essences for the spirit trade especially-Cognac essence (about 4lb. of essence for 100 gallons of spirit 10 under proof). Price 7s. per lb., free house, London, duty paid. Rum essence (about 4lb. of essence for 100 gallons of spirit 12 over proof). Price 6s. 6d. per lb., free house, London, duty paid. Gin essence, price 6s. 6d. per lb., free house, London, duty paid. We have been repeatedly highly complimented by the trade for producing such fine essences, and we venture to say that there are not similar essences in the market, that can compare with same.

"2. Every description of wine flavours, especially :-Port wine essence, at 3s. 9d. per lb., free house, London, duty paid. Sherry essence, at 3s. 6d. per lb., free house, London, duty paid, &c.

"3. Vegetable colours, in powder, guaranteed harmless for every purpose, we only mention :-Port wine colour at 3s. per lb., free house, London. Red wine colour at 2s. 9d. per lb., free house, London. Cognaccine colour at 20s. per lb., free house, London, a beautiful and rich colour for colouring brandies and spirits generally; its use will be found far more advantageous than adopting sugar colouring. Rum colour, for rum our R. E. colour will be found the most suitable. Price 20s. per lb., free house, London. It is equally rich, about eight drachms are sufficient for colouring one gallon of

fluid.

"4. Every kind of preparation, &c., for the clearing of dark and light wines, as clearing powders, gelatine, agar-agar, gelatine lime, terra di vino, &c.

"5. Every description of sugar colourings in casks of about 6 cwt. or 7 cwt., as: Rum colouring (in 40 o.p.), spirit colouring (in 58 o. p.), and wine colouring, 4s. 6d. to 7s. per gallon, free house, London.

"6. Gummitine.-A new article, being a substitute for the ordinary gum, especially suitable and highly recommended for sticking labels on glass, tins, etc. Price Is. 6d. per lb.

"7. We take this opportunity to bring to your notice our fruit juices, which we press on the premises, using only picked fruit for this purpose, as raspberry, blackberry, strawberry, red currant, cherry juice, &c.

"When in season, we supply these juices soon after pressing, and without any addition of spirit, and we shall be pleased to submit to you on application, a sample of any of them when ready. An early application is solicited.

"We specially draw your attention to our pure cherry juice. We press this juice from a specially selected sort of cherries. From the continually increasing demand of late years from England, we may consider that our juice has given general satisfaction. It has been found the simplest, best, and most advantageous means to prepare cherry brandy. This season's cherry crop does not promise to be a very abundant one, and we are, as yet, unable to give an idea of the price of the new juice, which may hardly be expected to be ready before the end of the current month.

"We shall be very glad to send you samples and quotations of any of our articles which may interest you, free of charge. We feel certain that a fair trial of our samples will convince you of the correctness of what we claim for our specialities.

"We are, dear Sirs, yours respectfully,

"DELVENDAHL AND KUENTZEL."

ORGANIC SYNTHESIS.*

BY S. G. JENKS.

HE history of chemistry might be styled "A Comedy of Errors," to constitute a true comedy. An error is not such a bad thing, however, as it is sometimes thought to be, for sooner or later someone finds it out and states the truth. Then follows a conflict between truth and error, in which truth is victorious. Thus truth is not only established, but emphasized.

The first error that affected the development of organic chemistry in a noticeable way was the search for the "philosopher's stone." At present we see the inorganic branch of the science far more fully developed than the organic, but this is not due to the greater age of the former. The ancients, naturally enough, I think, became acquainted with organic bodies first. They used acetic acid in the form of vinegar very early, while probably the earliest artificially prepared salts were the acetates of the alkalies. They were also acquainted with various gums, resins, oils, and sugar, and made wine from grapes, and beer from malted grain.

Why, then, did not the organic branch of the science keep ahead in the development? The answer is to be found in the fact that the search for the "philosopher's stone" led men to investigate inorganic substances to the almost total exclusion of organic bodies. However, after a time, the idea that there could be found an "elixir vitæ," a remedy for all the ills of the body, was joined to that of the "philosopher's stone," and this led to the investigation of organic bodies in their medicinal relations. This brings us to about the fifteenth century.

Still, in the next century those interested in the medicinal chemistry gave so large a portion of their time to mineral substances, that only a few organic compounds, as benzoic acid, wood vinegar, milk sugar, etc., can be found mentioned in writings of their times.

Another error just here served to separate the investigation of organic bodies from that of inorganic, and to give prominence to the latter. This was the belief that, while the composition of inorganic bodies could be determined by synthesis as well as by analysis, that of organic bodies could not. This belief was so enduring that Gmelin, in the first edition of his "Handbook," published in 1817, states that organic bodies cannot be built up by laboratory means from their elements; and about the same time Berzelius enforced the statement by a sentence in the introduction to his "Treatise," of which the following is a somewhat free translation. He says: "In living nature the elements appear to obey very different laws from those in inorganic nature; the products which result from the action of these elements differ from those with which inorganic nature presents us."

The veil thus thrown over the study of organic bodies was not lifted until 1828, when Wohler accomplished the artificial production of urea. This memorable event opened a new era in the study of organic compounds. Do not think, however, that this one discovery completely

A class essay read in the course in organic chemistry in the University of Michigan.-Pharm Era.

removed the errors just noted. This was only the beginning of a scientific conflict, and was not considered conclusive, since the urea was produced from ammonium cyanate, and this substance had not been prepared from its elements. Then, too, urea was a substance very easily decomposed into carbon dioxide and ammonia, and was only excreted from animal bodies, and must therefore, at most, be only semi-organic. We see to what extremities men will go to maintain a position once taken.

This discovery served to attract the attention of chemists to the subject, and other preparations followed. Then there came up various theories as to structure. The substitution of chlorine and other elements, known only in inorganic chemistry, for hydrogen, narrowed the gulf between organic and inorganic chemistry.

This last was carried to an amusing extreme in one case. Dumas had published his opinion that not only the hydrogen, but the nitrogen and oxygen in compounds containing these elements could be substituted by chlorine and still have a substance retaining the special properties of the original. This was too much for Liebig, who satirically replied that in manganous acetate he had replaced all the hydrogen, oxygen, and manganese, and finally the carbon, by chlorine, and that the resulting substance, although containing nothing but chlorine, retained all the characteristic properties of manganous acetate.

Let us take the following as an example of complete organic synthesis. Vapour of sulphur passed over glowing coke yields carbon disulphide. A mixture of iron and sulphur heated yields ferrous sulphide, and this treated with hydrochloric acid, whose elements need only sunlight to unite directly, yields hydrosulphuric acid. Pass a mixture of hydrosulphuric acid and carbon disulphide over red hot copper, and we have marsh gas. Treating this with chlorine, gives chloroform, which, when heated with potassium hydrate, yields methyl alcohol easily oxidizable to formic acid. This gives the list of methyl compounds by synthesis, and others are as easily prepared.

Thus it is proved that the indefinable agency which we call life does not supersede chemical force, but that the latter operates in the presence as in the absence of the former. This statement does not argue that there is no such agency as life, but rather that the author of both vital and chemical forces does not allow one to usurp the dominion of the others.

THIS

TURKEY RED OIL.

HIS article treats of the conditions necessary for successful application of the " Sulphated Oil Process" in dyeing cotton with alizarine red. All recipes for preparing the oil agree in requiring the sulphuric acid to be added very slowly to the oil and with constant stirring, in order to avoid heating during the mixture and the evolution of sulphurous acid in any large quantity. The author describes experiments which demonstrate that the risk of spoiling the product is much less than is commonly supposed. He shows that at temperatures below 70° any evolution of sulphurous acid must be due to albuminoid substances present as impurities in the oil, the oil itself not giving rise to sulphurous acid below that temperature. (The paper is practically confined to the treatment of castor oil, as that is the only one in common use in Russia for Turkey-red dyeing.) The endeavour to avoid any evolution of sulphurous acid may even lead to very imperfect results being obtained, for a low temperature of reaction will leave much of the oil undecomposed-the author's view being that only the fatty acid is of use in the dyeing process. In working on the large scale with 1,000 kilos. of castor oil the author adopts the following procedure. In winter 20 to 30 per cent., and in summer 15 to 20 per cent. of concentrated sulphuric acid are used. About one half of the acid is stirred into the oil during 9 hours of the working day and the mixture is allowed to stand over-night. On the next day the second half of the acid is stirred in and the mixture allowed to stand until a sample gives a clear solution when diluted with water in a test-tube. The bulk is then mixed with an equal weight of water. It is necessary to test a sample frequently, as the mixture will give a cloudy solution in water if either too short or too long a time be given for the reaction. The proportion of free fatty acid may be increased if desired by using hot water for dilution. On allowing the mixture to stand, the oily part separates and floats on the aqueous acid layer, and it is drawn off to be treated with alkali. As some of the best preparations contain only 2 to 5 parts of SO3 to 100 parts of fatty acids, whereas the sulphonated fatty acid should contain 6 to 15 times more SO, it is evident that the sulphonated fatty acid is not of essential importance, and this conclusion is corroborated by an experiment on the large scale in dyeing with fatty acid prepared by saponification with alkali, in which, of course, no sulphonated compound was present; but al though the shade produced was very fine, the oil bath showed a tendency to frothing, which caused the dyeing to be somewhat uneven. In order to fit the sulphated castor oil for use as a mordant, it has to be partially neutralized by an alkali, and the author finds that

sufficient alkali has been added when it amounts to more than a quarter and less than half that required for theoretical neutralisation. In practice the alkali, either caustic soda or ammonia, or both, is added to the emulsified fatty acid until the mixture becomes suddenly clear, when the right degree of neutralisation has been attained.

The use of ammonia for neutralisation has certain advantages, especially in the finishing and printing of steam colours, because the alkali volatilizes and leaves only the free fatty acid on the cloth. The reason why castor oil has come to be selected as the most suitable for Turkey-red oil dyeing is its property of forming a soluble soap with a minimum proportion of alkali. Solutions of other fatty acids give emulsions rather than clear solutions when the proportion of alkali falls much below that required for complete neutralisation. Again, the decomposition of the oil by the action of sulphuric acid is more complete with castor oil than with any other oil which can be used, and maximum decomposition is essential to the achievement of the best results. A certain proportion of undecomposed oil has, however, the advantage that it lessens the tendency to frothing, and the decomposition by means of sulphuric acid in the case of castor oil provides for the ready attainment of this condition.-Dingl. Polyt.

ON THE POLLUTION AND SPONTANEOUS PURIFICATION OF RIVERS.

A1

T the annual meeting of the German Society of Gas and Water Engineers and Chemists, which was held at Munich in June, Professor V. Pettenkofer delivered an address on the pollution and spontaneous purification of rivers, which will no doubt be of interest to our readers. The address was of special importance to the inhabitants of Munich, because a sewer is being laid down throughout a portion of the town, which opens directly into the Isar, the sewage not being filtered or treated in any way.

The problem of the spontaneous purification of rivers, can only be considered from the theoretical point of view, and each case has to be considered on its merits, since general rules cannot be laid down. That the admission of sewage to a river can actually take place without injury to the dwellers on its banks is proved by many instances, among others by that of the Tiber, into which the Cloaca Maxima (made in 600 B.C.) opens, without doing any harm to the inhabitants near the river. The water of the Elbe, moreover, is drinkable at Altona, although the sewage of Hamburg has been run into it for forty years In the same way no impurities have been detected in the lower waters of the Isar, although the sewage of Munich has hitherto always found its way thither.

As long as only "dirty water" and "wash water were spoken of no objections were raised, but the word "sewage" has recently caused considerable opposition to the new scheme. Soxhlet has in the meantime shown that at the present date almost 80 per cent of the total sewage finds its way into the Isar. With the present population of 280,000, the organic matter of urine and fæces amounts to 6 milligrammes per litre of water, so that even if spontaneous purification did not take place, no injury could arise with such great diliation. If the population were even doubled, the amount would only be 12 milligrammes per litre. The lecturer showed flasks containing pure water and water containing the quantity of sewage mentioned above, which appeared to be equally clear. It is chiefly due to imagination that water which is perfectly clear is rejected as unfit for use because sewage has been mentioned in connection with it. It must be remembered that no water is absolutely pure, just as the air is not perfectly pure, and yet we manage to live in it very comfortably. Only impurities whose amount can be determined need be seriously considered.

Another source of fear is the tribe of bacilli, which has only recently become known to the generality of people, but of which only the pathogenic members are to be feared. Water which is as clear as crystal, may, nevertheless, contain these. Although the lecturer himself formerly expressed the opinion, that infectious diseases follow the river courses, yet he considers this arises from the underground water, since diseases sometimes spread, not down, but up a river valley. The hos pitals and slaughter-houses of Munich have long been drained into the Isar without any evil effects being traced to them. The same is true of Würzburg, where the Julius hospital is drained into the Maine. The bacilli and bacteria in the water, which are invisible to the naked eye, are so minute that 30 millions of them, after drying, only weigh one milligramme. A few miles below Munich, only 92 per cent. of the bacilli found in the Isar near the town, are still present, a proof that something in the course of the river tends to destroy them. Similar observations have been made between Geneva and Lyons on the Rhine, and near Basle. The disease germs soon die in pure water, partly be cause they fail to obtain sufficient nourishment, and partly on account of the struggle for existence in the presence of the much more numerous harmless bacilli. Although the cause of this spontaneous purification of

one.

rivers still requires explanation, the phenomenon is a well established The amount of water in the river does not seem to be so important a factor in producing it as the rate at which the river flows. Taking the average rate as o'7 metres per second, that of the Isar is 1'2, and that of the Spree, about 0'5. This explains the enormous numbers of bacilli which are found in the last named river below Berlin. It appears, therefore, that although it is necessary in some large towns to keep the sewage out of the rivers by means of filteration fields, this costly arrangement is not invariably necessary, and that, in many cases, sewage can be run directly into a stream without any injury being done to the inhabitants on its lower banks.-Chem. Zeitung.

MAC IVOR'S PATENTS, LIMITED.

APPLICATION FOR AMENDMENT.

Torested to learn that Messts. Ralph Waldo Emerson Mac vor,

HOSE of our readers who are concerned with white lead may be

Frederic Arthur Darlington, Gavin Paul, John Allan, John Byron Umpleby, Leonard Grant, Walter Herbert Cook, Ellis Lever, and Harry William Christmas have applied for leave to further amend the Specification of Letters Patent No. 10.426, 18th July, 1888, granted to Ralph Waldo Emerson Mac Ivor, "For Improvements in the production of white lead or carbonate of lead and the apparatus therefor," alleging as their reasons that: "We desire to disclaim the use of all alkaline acetates (other than acetate of ammonia), as these bodies cannot be employed with advantage. Also we desire to correct certain clerical errors, and to amend certain expressions with a view to render the Specification more accurate and clear." The amendments proposed are as follows:--

THERE are now in Chili no less than 45 works for the production of nitrate of soda, as we learn from the firm of J. Zayas & Co., who are large manufacturers in Iquique, and to whom our thanks are due for the detailed information with which they have provided us on this subject. The various companies combined, until 1887, to regulate production, but many of them had exaggerated their capabilities so as to obtain a larger share in the division of the total production than ought really to have accrued to them. This is at once evident when we examine the detailed statements of the officially declared capability of the company and compare it with the actual production as represented by the exportation during 1888. Certain firms, such as Messrs. Gibbs & Co., whose works have just been purchased by companies of recent formation, produce only about onehalf of the amount declared to committee of the syndicate, and others only 11'43, 1298, and even 8.75 per cent. of their declared production. This state of affairs was abnormal, and injured the large works, and it was this that brought about the abandonment of the syndicate. It is true that the companies could, without doubt, increase their production, but the evidence clearly shows that the productive power of the works was exaggerated in the declarations made before the committee. The formation of a new syndicate is already rumoured. -L'Engrais.

BORINGS FOR SALT AND COAL NEAR SOUTHPORT.-During the past few weeks, a company of gentlemen have been superintending boring operations at Barton Moss, about seven miles from Southport. Their first object was the finding of salt, which they believed existed in the neighbourhood. This, it is said, they have found, but in excavating deeper in some places they have come upon seams of coal, and it is supposed that it abounds in the neighbourhood.

Analytical Notes.

NEW TEST FOR TANNIN.

C. BOTTINGER has proposed a new test for tannin, which depends upon its reaction with phenylhydrazin. If a little tannin is heated with double its weight of phenylhydrazin for a few minutes to a temperature slightly over 100° C., a little water added, and the whole boiled for a few seconds, and then allowing a drop or two to fall into a large beaker containing water made alkaline with caustic soda, a beautiful blue colouration is developed, which gradually subsides into yellow. If gallic acid is treated in the same way, an orange or golden yellow is produced.

TESTING GUM ARABIC.

Professor Leo Liebermann communicates to the Chemiker Zeitung a paper on the examination of gum arabic, in the course of which he states that both Senegal and Cordofan gums should dissolve completely in lukewarm water, whereas cherry-tree gum only partially dissolves, or, at the best, swells up in the water. When the solution is treated with large excess of potash solution. and copper sulphate, warmed slightly (not boiled), and filtered, the filtrate and the precipitate may be reserved for examination. The filtrate will contain dextrin if any has been present in the sample, and on boiling it the characteristic brick-red precipitate of cuprous oxide will be formed should that be sc. The precipitate formed by the Fehling's solution in the first instance gives the data for conclusions regarding the nature of the gum proper. After washing with distilled water, dissolve in dilute hydrochloric acid and precipitate with a large excess of alcohol. Allow the precipitate half a day or a day to settle, collect it, dissolve in water, and again precipitate with alkali and copper, purifying with hydrochloric acid and water as before. If the sample is pure gum arabic it is noticed that the precipitate thrown down by alcohol gathers into one lump, and a little of it dissolved in water and boiled with solution of potash gives an amber-coloured solution. The gum-senegal precipitate, on the other hand, does not agglomerate, and it gives no colour, or only a straw colour, when boiled with alkali; but if the precipitate does not agglomerate, and gives an amber colour with alkali, the sample is a mixture of gum arabic and gum senegal. It is also noticeable that the blue copper-precipitate formed on adding alkali and copper to the watery solutions of the gums is more abundant in the case of true gum arabic than in the case of gum senegal-indeed, in the latter case the precipitate is not at all abundant.

A

BISULPHIDE OF CARBON.

CORRESPONDENT writes :-An interest of a very practical kind attaches to this compound. Carbon bisulphide (Fr., sulphure de carbone) is a colourless, heavy, very mobile and volatile liquid. It is made by the action of sulphur vapour on red-hot charcoal, and is used in the manufacture of waterproof materials, the extraction of oils from seeds, etc. It has a specific gravity of 129, and boils at 1148 deg. F., but volatilizes very quickly at ordinary temperatures. The specific gravity of the vapour is rather more than 21⁄2 times that of atmospheric air, and the vapour not only readily collects near the bottom of any space in which it is produced, but flows along almost like a fluid, and the vapour may thus reach a fire and be inflamed at some distance from its source of production. One of the most striking characteristics of this vapour is the extremely low temperature at which, when mixed with air, it takes fire. According to experiments, this temperature is about 415 deg. F. (some authorites give it considerably lower). If it is borne in mind that the lowest visible redheat corresponds to a temperature of about 1,200 deg. F., while a bright red-heat, such as is necessary to inflame a mixture of benzolene vapour and air, corresponds to about 2,100 deg. F., it will be seen how very low, relatively speaking, the temperature of ignition is in the case of bisulphide vapour. The smallest spark from iron, a fire, a cirder after it has lost all appearance of fire, an even moderately heated stove, etc., are hot enough to set it on fire. The mere striking together of two pieces of iron within the inflammable atmosphere is sufficient to ignite it. It is not essential that an actual spark should be produced in order to bring about this result, but if the particle struck off is about 415 deg. F., a temperature far below red heat, ignition will result. The above is an abridgement of the evidence of Dr. A. Dupré, taken for the purposes of a recent Board of Trade inquiry into the burning of the Livadia, a Liverpool steamer, which was laden with 150 tons of sulphure de carbone, and with other cargo, at Marseilles, and had to be abandoned by her crew off Cape Cette on May 11 last. inspector appointed by the Board thought the casuality due to the leakage of one of the drums in which the sulphure was stored, to the formation of vapour, and to its being drawn up the drain pipes through the scuppers, so that it came into contact with a light in the forecastle.

The

WHISKEY FROM JUTE!

THE HE revelations recently made before a Select Committee of the House of Commons as to the substances from which some of our modern distillers obtain their whiskey were astounding to many who had not previously heard that potatoes can be utilised for the production of that alcoholic drink. But hundreds of others knew all about it long before the Select Committee published the result of its enquiries. Thousands of barrels of beer brewed in this country are guiltless of hops. This also is a fact not unknown to the multitude. But who in the name of all that is wonderful would ever dream that whiskey can be produced from jute? Very few surely. And yet the statement is made in all seriousness by a reputable commercial journal published at Lille, that the intoxicating drink is obtained from this Eastern textile. The process is so repulsive that one shudders at the rascality of the unscrupulous rogues who do not hesitate to poison a whole community with their vile preparations in order to enrich themselves. The authority mentioned says that endeavours have been made to utilise the saccharine and other constituents of jute for the making of a kind of comestible glucose by the aid of sulphuric acid, or by fermentation, a jute whiskey (wiskey de jute) similar in taste to the eau de vie de grains. Temperance lecturers who wish to disgust their audiences with the brewing and distilling fraternity might with advantage refer to the process of producing wiskey de jute. The next thing we may possibly hear of will be beer from cotton or rum from flax, if this jute whiskey really exists.-Textile Mercury.

ON THE MANUFACTURE OF DYE-WOOD EXTRACTS.

THE articles which have been recently published on this subject by Messrs. Soxhlet and Brühl have already excited attention among the German houses connected with this trade, and the following criticism has been sent us by Herr Beyerbach :

Assuming that the papers referred to above are meant to be looked at from a practical point of view, I must remark that the conclusions which they lead up to are rendered uncertain by a slight vagueness in the assumptions upon which they are based. The determination of the yield of logwood extract by the ordinary rules of percentage is inadmissible, and, considering the extraordinary variety of the raw material, it is not to be wondered at that the two authors do not agree on the point. They also differ in their mode of examining a wood extract, and, therefore, in their valuation of it, and this is actually the main difficulty, since chemistry has not yet devised a scientifically accurate method of determining the strength of wood extracts. Herr Soxhlet assumes that greater concentration leads to a correspondingly greater strength, and, therefore, decides unconditionally in favour of the American process. In this, however, he is undoubtedly in the wrong, and forgets the numerous applications of the extract, which admit of and even require various qualities. The lowering of quality caused by the fall of prices has little to do with science, but always renders work more difficult. It is to be hoped that the consumers will gradually begin to realise that the honesty of the manufacturer is of more importance to them than small differences of price.

The charges made by both authors against the German extract industry seem to assume without hesitation more scientific knowledge among the competing manufacturers in America and France. This is quite inaccurate, as is also the statement that the German manufacturers make very little use of chemistry in this trade. I am acquainted with a number of extract makers who are quite familiar with this science, and readily call in its assistance, in spite of its comparative weakness in this particular branch. I believe that many of these men could easily show the complete injustice of the charges brought against them by Messrs. Soxhlet and Brühl if their own interest did not restrain them from publishing the advantage which they have laboriously worked out for themselves. It may also be observed that in recent years a steady decrease in the importation and an increase in the exportation of extracts has taken place. The supply of raw material to Germany has also considerably increased, a fact which points most unmistakeably to the growth of the industry. This advance has been made under very unfavourable conditions, since America and France can send the excess of their production to Germany almost unhindered by the duty of 3s. per 100 kilogrammes, while both the countries by a very high protective tariff prevent the German manufacturers from taking their revenge. Moreover, it must be borne in mind that in both these countries the manufacture has been long established, whereas it has only been adopted at a comparatively recent date in Germany.

Some of the German manufacturers who have reliable scientific men at their disposal give to these the greatest influence on the development of the industry.

Chance expressions of opinion to the contrary, such as that which recently occurred in the Leipzig trade report on the drying of furs (an industry of comparatively small importance) should not be so invidiously circulated. For my own part, I shall continue to endeavour to find opportunities to overcome opposition, wherever it may exist, by showing by practical tests the insufficiency of the grounds upon which it is based.

The progress already made will undoubtedly be further increased, especially if the still youthful industry be aided by an increase in the protective duty.-Chemiker Zeitung.

R

EFRIGERATING machinery may be conveniently divided into two classes. In the first we have the large machines such as are used for freezing cargoes of meat, and in abbatoirs, as also for the production of ice in considerable quantities. The second class is composed of those machines, less imposing, but not less useful in their way, which are adapted to meet the thousand and one requirements of every day life. Of this class we commend the "Champion" Ice Making Machines of the Pulsometer Engineering Co., Ltd., London, to the notice of our readers. The general features of these machines may be gathered from the accompanying illustration of the No. 2 size. They are constructed on the well known principle that water will freeze when rapidly evaporated by means of a vacuum pump, and simultaneous absorption of the liberated aqueous vapour by some powerful absorber such as sulphuric acid.

The machine consists essentially of a powerful vacuum pump, shown on the left of the figure of the absorbing vessel fixed to the base, and containing sulphuric acid, and the glass vessel shown above the absorber, to contain whatever is required to be frozen or cooled.

The pump is the most important part of the machine. It will produce a practically perfect vacuum, though worked at a slow and easy stroke (particularly as the air becomes more and more rarefied), and it is impossible that air can leak through the pump, though it should stand for any length of time.

There is no fine mechanical fitting about the pump, and all the working parts being quite free and easy, the friction is reduced to a minimum, and as the machines are handy and moderate in cost, they should meet with a large sale.

251093A