Both the coca used and the fluid extract were then assayed by the modern methods, for the proportion of the alkaloid they contained.
The only assays of coca that could be found conveniently were those of Dr. Albert Niemann, of Goslar, given in the American Journal of Pharmacy, vol. xxxiii., p. 222, who obtained 0.25 per cent.; and of Prof. Jno. M. Maisch, in the same volume of the same journal, p. 496, who obtained 4 grains of alkaloid from 1,500 grains of coca, which is also about a quarter of one per cent. These assays were, however, very old, and made by the old process. The process used by the writer was the more modern one of Dragendorff slightly modified. It was as follows:
Thirty grammes of powdered coca, thoroughly mixed in a mortar with 8 grammes of caustic magnesia, were stirred into 200 c.c. of boiling water, and the mixture boiled for ten minutes. The liquid was filtered off, and the residue percolated with about 60 c.c. of water. It was then again stirred into 150 c.c. of boiling water, and was again boiled and percolated until apparently thoroughly exhausted. The total liquid, amounting to more than 600 c.c., was evaporated on a water-bath, commencing with the weaker portions, so that the stronger ones might be exposed to the heat for the shortest time, until reduced to about 20 c.c. This liquid extract was transferred to a flask, and vigorously shaken with 50 c.c. of strong ether. The ether was poured off, as closely as practicable, into a tared capsule, where it was allowed to evaporate spontaneously. A second and third portion of ether, each of 50 c.c., were used in the same way, and the whole evaporated to dryness in the capsule. A scanty, greenish, oily residue was left in the capsule, in which there was no appearance of a crystallized alkaloid. The capsule and contents were then weighed and the weight noted. The oily residue was then repeatedly washed with small quantities of water, until the washings no longer affected litmus-paper. The oily matter adhered to the capsule during this process, no part of it coming off with the washing, and at the end of the washing the capsule and contents were again dried and weighed, and the weight subtracted from the original weight. The difference was taken as the alkaloid cocaine, and it amounted to 0.077 grm., equal to 0.26 per cent.
Several preliminary assays were made in reaching this method. Some authorities recommend the very finely powdered mixture of coca and magnesia, or coca and lime, to be at once exhausted with ether. Others recommend that the mixture be made into a paste with water, and after drying on a water-bath that it be then exhausted with ether. This is better, but neither of these methods were satisfactory.
Finally, 30 c.c. of a well made fluid extract of the same coca was thoroughly mixed with 8 grms. of caustic magnesia in a capsule, and the mixture dried on a water-bath and powdered. This powder was then exhausted, one part by ether and the other part by chloroform, exactly as in the method given, both parts giving very slightly higher results. As a check upon the results, the solution of alkaloid washed out was titrated with normal solution of oxalic acid.
From all this it would appear that this inferior coca of the markets, or rather the best that can be selected from it, yields about the same proportion of the alkaloid as was obtained by Niemann and Maisch, but it has been shown that, by the older processes of assay used by them, much of the alkaloid was probably lost or destroyed, and that much better results are generally obtained by the modern process.
Now, since 3 drachms of this coca, or three fluid drachms of its fluid extract, gave the same physiological, or perhaps therapeutical, effect as 3 grains of caffeine, and as the 3 drachms contained about 0.45 grain of cocaine, it follows that cocaine is about 6.5 times more effective than caffeine; but it also follows that the coca accessible, and even the very best coca, contains very much less of its alkaloid than those articles which yield caffeine do of that principle.
From an "Ephemeris of Materia Medica, Pharmacy, Therapeutics, and Collateral Information." By Edward E. Squibb, M.D., Edward H. Squibb, S.B., M.D., and Charles F. Squibb, A.B.