The last statement would lead one to expect the presence of available iron and cyanogen ions. In fact, the inference to be drawn from all the company’s “literature” is that “hydrocyanate of iron” is a definite chemical compound in the same sense as is ferrocyanid of iron, and that inference is still further borne out in the letter to our correspondent. This being the case, the Tilden Company was again written to and asked for the chemical formula of “hydrocyanate of iron,” with the following result: “Replying to your inquiry regarding the formula of Hydrocyanate of Iron we beg to state the composition of this preparation is a trade secret and we therefore do not care to furnish the desired information.” This reply verified the opinion already formed that “hydrocyanate of iron” is a secret preparation. Its analysis was then taken up in the Association’s laboratory. EXAMINATION OF THE TABLETS The product appears on the market in cartons said to contain one ounce of one-grain tablets. On the cartons, in addition to the name of the preparation and the name and address of the manufacturers, are the names of diseases for which it is recommended. The tablets, in the specimens analyzed, were dark blue, rather hard and slightly bitter in taste and had an average weight of 0.1382 gm., or about 2 grains. They were found to be practically insoluble in water and dilute mineral acids; aqueous oxalic acid solution partially dissolved them, yielding a blue solution. Boiling with alkali hydroxid solution decomposed the tablets, yielding iron in an insoluble form and a solution of alkali ferrocyanid, as demonstrated by the appearance of a deep blue precipitate on the addition of ferric chlorid solution. The portion insoluble in alkali when boiled with hydrochloric acid yielded a solution containing iron, approximately equivalent to 50 per cent. Prussian blue. These properties are all characteristic of Prussian blue, and, taken together, identify Prussian blue as a constituent of “hydrocyanate of iron (Tilden).” The insoluble residue from the iron determination possessed the properties and constituents of talc and constituted practically one-half of the tablets. Extraction of the tablets with chloroform or ether in the presence of ammonium hydroxid yielded a small amount of organic material which contained bodies having the properties of, and responding to tests for, quinin or cinchona alkaloids and caffein. The presence of a salicylate was also indicated.[95] [95] Details of the quantitative analysis of “Hydrocyanate of Iron--Tilden” appear in the annual report for 1909 of the Chemical Laboratory of the American Medical Association.