In closing, I should like to express my thanks for this opportunity of calling the attention of the American Philosophical Society to this unpublished diary of one of its former members,10 who must have spent, as indeed its proceedings show, many delightful evenings in its halls and who with pride placed after his name upon the title pages of his well-known works "Member of the American Philosophical Society."

When he sailed upon the voyage which was to take him back to the country and to the people he loved, Moreau de Saint-Méry must have left in this society many friends who thoroughly appreciated his great talents and who had been attracted by his interesting personality. It is fortunate that such a man left for us a record of his sojourn in America and that it is possible to rescue it from the dust of archives.11

10

1o Moreau was elected to the society on January 16, 1789, before he left France. The records show that he attended its meetings regularly after his arrival in Philadelphia in the fall of 1794.

"The diary will be published in the near future at the Yale University Press.

THE CLASSIFICATION OF CARBON COMPOUNDS.

BY MARSTON TAYLOR BOGERT.

(Read April 20, 1912.)

The system of classification adopted for a science at any given period registers quite accurately the state of the science at that period, and the changes in the classification therefore record its progress. It is, hence, practically impossible to give any intelligible description of the various methods of classification which have been employed for carbon compounds without at the same time sketching briefly the changing conceptions and theories of which they were to so large an extent the natural reflection, for without such a setting the picture would have no proper background or perspective.

The classifications which are considered are particularly those which have been used for textbook instruction in organic chemistry, and no place is given to those which have been devised solely for the patent offices, for reference, or for other special purposes.

Man being naturally of an inquiring mind, he has probably speculated upon the composition of this world of ours ever since he first appeared upon it, for in the oldest records we find theories concerning the elements of which it is composed.

The doctrine of the four so-called "elements "-earth, air, fire and water-was first enunciated in Greece by Empedocles, about 440 B. C., but generally bears the name of Aristotle. Neither Empedocles nor Aristotle regarded these elements as different forms of matter, but rather as different properties or manifestations of one original matter. Aristotle also added a fifth element, ovo ía, to which he ascribed an ethereal or immaterial character and which he assumed permeated the universe. As the oldest writings of India contain a similar theory of four elementary principles and an ethereal substance, it is possible that both Aristotle and Empedocles

were familiar with this fact and were only introducing into Greece this ancient Indian theory.

The oldest nations were familiar with the metals and refer to them frequently in their writings, but it should not be forgotten that some of the earliest chemical facts on record have to do with carbon compounds. The only acid known to the ancients was acetic (as vinegar), so that the name of this substance and the idea of acidity were expressed by closely related words; in the Greek, oos for vinegar, and oğús for acid; in the Latin, acetus and acidus. The first reagent of any kind mentioned was the extract of gall nuts, which Pliny says the ancients used to detect the presence of green vitriol in verdigris. The first salts artificially prepared were those obtained by the action of vinegar upon alkalies. The first crude attempts at distillation were with turpentine. The ancients were familiar also with fats, resins, organic coloring matters (like indigo. and Tyrian purple), sugar, gums, the preparation of wine from grape juice, of beer from malted grain, of mead from honey, of soap from fats, and many other facts in these and related fields. Organic chemistry, therefore, does not give place in point of age to inorganic. Largely due to the influence of Alchemy, however, the object of which was the transmutation of baser metals into silver and gold, the mineral side of the subject was the first to be extensively developed.

According to the pseudo-Geber, all metals consisted of sulfur and mercury, in varying amounts and in different degrees of purity. The old Aristotelian "elements" he appears to have regarded as subsidiary constituents, or perhaps as the ultimate components of the sulfur and mercury. To the pseudo-Geber's two elements, Basil Valentine added a third, "salt," not meaning any particular compound but the properties characteristic of common sodium chloride, and he assumed these three to be the elementary constituents not only of metallic substances but of organic as well; sulfur endowing the substance with combustibility, or the property of changing in the fire, and also explaining color changes, mercury giving metallic properties and volatility, and salt representing the principle of solidification and of resistance to fire.

PROC. AMER. PHIL. SOC., LI. 205 N, PRINTED JULY 24, 1912.

In spite of the great amount of experimental work carried out by the alchemists, and the large number of new facts discovered by them, their writings were so obscured by mysticism, exaggeration and deceit, that little real progress was made toward a more accurate understanding of the nature of chemical compounds which might be utilized in constructing a more satisfactory method of classification. No attempts were made to determine the actual constituents of compounds, for it was assumed that in the formation of a compound the original substances were annihilated and an entirely new substance created. Hence the only classification in vogue was a rough grouping of substances according to their physical properties, or apparent outward resemblance, and many of our common names are reminders of this bygone empirical method. Thus, olive oil and other vegetable and animal oils were grouped with oil of vitriol and oleum tartari (deliquesced potassium carbonate); spirit of wine (alcohol) with fuming spirit of Libavius (stannic chloride), spirit of hartshorn (ammonium hydroxide solution) and spirit of nitre (nitric acid); butter with butter of antimony (antimony trichloride) and other semi-solid metallic chlorides. Colorless solids, soluble in water and of characteristic well marked taste, were all classed as "salts," and this group thus included sugar.

The goal toward which the alchemists strove was the philosopher's stone, the grand elixir or the magisterium, as it was variously called, whose virtues were such that it could not only transmute baser metals into silver and gold, but could also prolong life indefinitely. As the claims concerning the transmutation of metals were increasingly discredited and the trickery and deception of the alchemists exposed, more investigators directed their attention toward the second great function of the philosopher's stone, the prolongation of life, and many compounds were discovered of considerable therapeutic value. Great interest was aroused by these investigations, and Paracelsus finally announced that "the object of chemistry is not to make gold but to prepare medicines." Thus, in the first half of the sixteenth century, chemistry began to develop in a new direction, at first not far removed from alchemy, but gradually diverging from it more and more widely, and approaching closer and closer

to medicine, until the coalescence of the two sciences appeared practically complete. And thus arose the period of iatro chemistry, when chemistry, which had long been looked upon as a valuable helpmeet to medicine, came to be regarded as the basis of the entire medical art.

Although in this period the chief development was again along the mineral side, probably because of the relatively greater simplicity and stability of these preparations, still no little organic investigation was conducted and a number of new compounds were added to the science. Little progress was made in gaining a truer insight into the character of chemical compounds, and hence no important changes in classification appear. Paracelsus himself, the founder of the iatro-chemical school, adopted Basil Valentine's three elements (sulfur, mercury and salt) as the basis of his doctrines.

By the middle of the seventeenth century, chemistry awakened to the fact that it had a destiny of its own to realize, struggled to its feet and, refusing longer to be supported by other sciences, started forward, to be sure rather unsteadily and uncertainly at first, but with the firm determination to do something for itself.

The history of chemistry proper begins with Robert Boyle about 1660, who taught that its main object was the determination of the composition of matter. Through his labors, and those of Rouelle and others, the terms "element" and "chemical compound" were more fully explained and appreciated; nevertheless many of their colleagues still adhered to the old alchemical or even the Aristotelian elements. Kopp, in his "Geschichte der Chemie," gives an excellent picture of the epoch-marking effect of Boyle's ideas:

"What a contrast is exhibited between the ancient idea of the cause of difference in various forms of matter and that which obtained at the time of Boyle! If we consider these two opposite conceptions historically, and the transition from the one to the other, they appear like two totally dissimilar pictures; but, like dissolving views, changing the one into the other by slow degrees. In the first place we have the Aristotelian idea, according to which, matter itself devoid of properties, becomes endowed with characteristic qualities by the addition of properties, and forms, when invested with these properties, the various substances known in nature; then this idea passes gradually into that of the alchemists, but becomes confused in the transition, inasmuch as the differences of physical condition and properties are no