Hydroferrocyanic acid

The portion of the report here omitted refers to Kitaibel s paper on hydroferrocyanic acid and Prussian blue.]... 

Then you came to Vienna, obtained from Estner my article on the investigation of the so-called silver molybdenite and another one on hydroferrocyanic acid prepared in the free state, for your opinion, and Estner sent me your written verdict with the information that he had also communicated to you my report on the metal which lay hidden in Transylvanian gold ores and had requested you to investigate the matter further. I rejoiced over this all the more because I had good reason to hope that, when you announced your investigation, you would mention my work. 

Properties of Potassium Ferrocyanide (SECTION 240).— (a) Conversion into hydroferrocyanic acid.—Add concentrated hydrochloric acid to about 10 cc. of a saturated solution of potassium ferrocyanide as long as a precipitate is formed, (Eq.) Pour off the liquid and place a part of the crystals on a porous plate. They turn blue due to oxidation. 

Hydroferrocyanic Acid. A peculiar compound of cyanogen, hydroeeu, and iron, discovered by M. Forret, and called by him ferrochyasic acid. It consists of... 

To Obtain Hydroferrocyanic Acid, It may be obtained from a concentrated boiling solution of ferrocyanido of potassium, cooled out of contact with tho air, and muriatic acid added in excess. Tho mixture is then agitated tvith a little ether, which separates tho acid the latter is collected by filtration, and dried. 

The insoluble cyanides dissolve in solutions of potassium cyanide, and double salts are formed. These belong to two classes those which are readily decomposed by dilute acids in the cold and yield hydrocyanic acid, and those which yield complex acids. When, for example, the double salt of the formula KAg(CN)2 is treated with an acid, silver cyanide is precipitated and hydrocyanic acid is formed as the result of the action of the acid on potassium cyanide. When, however, potassium ferrocyanide, K4Fe(CN)6, is treated with an acid, a simple double decomposition takes place and hydroferrocyanic acid is formed —... 

II. A Mixture of Potassium Ferrocyanide and Acetic Acid,— The precipitation is produced as the result of the formation of hydroferrocyanic acid, which forms an insoluble compound with the protein. The reaction is used clinically as a test for albumin. Hydroferrocyanic acid gives but a faint precipitate with gelatin, and does not precipitate peptones. 

Paul Kitaibel (Mattersdorf, Hungary, 3 February 1757-Budapest, 13 December 1817 (or 1818) other dates are given) was professor of chemistry and botany (1802-1811), then of botany and director of the Botanic Garden in Buda Pest. He never lectured and made (at the cost of the University) extensive scientific travels in Hun> gary. He is said to have discovered solid chloride of lime, hydroferrocyanic acid, platinum black, and metallic soaps. ... 

---