March l, 1865.] THE TECHNOLOGIST. 



ON CHEMISTRY APPLIED TO THE ARTS. 349 



Bouchard for obtaining salts of cyanogen from the ammoniacal waters 

 of gas-works ; those of Mr. R. T. Hughes and Messrs. Bramwell, of 

 Newcastle, for the conversion of nitrogen of the atmosphere into cyanide 

 of potassium ; that of M. Kamrodt, for decomposing ammonia by carbon 

 carried to a high temperature ; and lastly, that of MM. Marguerite and 

 De Sourdeval, for producing cyanogen from the nitrogen of the atmo- 

 sphere and fixing it by means of barium. This latter process seems to 

 be highly commended by the learned reporter to whom I have referred. 

 I must not, however, omit to mention the scientific and interesting pro- 

 cess devised by Mr. Gelis, and based on the chemical reaction which, 

 ensues when bisulphide of carbon is mixed with sulphide of ammonium. 

 Yellow prussiate crystallizes in large crystals belonging to the pctohe- 

 dral system, composed, as before stated, of two parts of cyanide of po- 

 tassium, 2 Cy K, and one of iron, Cy Fe + 3 of water or H 0. This 

 salt is freely soluble in water, but is insoluble in alcohol, and when 

 mixed with weak vitriol and heated gives rise to prussic acid, which 

 distils, and may be used either as a violent poison or, in qualified hands, 

 as a most valuable therapeutic agent. When ferrocyanide of potassium 

 is heated with several times its bulk of concentrated sulphuric acid, 

 instead of yielding prussic acid, as above, it gives rise to a poisonous gas, 

 called oxide of carbon, which burns with a beautiful blue flame, and 

 which we have all seen burning in our fireplaces when the combustible 

 matter has lost all its volatile constituents and nothing remains but a red 

 incandescent mass. When chlorine is passed through a solution of this 

 salt chloride of potassium is formed, and the yellow prussiate is con- 

 verted into red prussiate or ferrocyanide of .potassium, composed of 

 3 Cy K + 3 Fe 2 Cy 3 . When heated with peroxide of mercury, potash, 

 peroxide of iron, and cyanide of mercury are produced, the latter being 

 a most violent poison. To produce Prussian blue on silk with this salt, 

 all that is required is to dip the silk in a slightly acidulated liquor con- 

 taining a persalt of iron, and when the silk is washed and mordanted, 

 it is dipped in a weak acidulated solution of yellow prussiate of potash, 

 when it assumes a beautiful blue colour, due to the formation of Prussian 

 blue. To dye wood it is necessary to pass it through a boiling bath 

 composed of yellow prussiate, muriate of tin, and a small quantity of 

 sulphuric acid. Prussian blue is gradually formed, and fixes itself on 

 the fibre. To produce blue on calicoes, a solution of yellow prussiate 

 of potash is made, to which is added some tartaric acid and muriate of 

 tin. This mixture, after having been properly thickened, is printed on 

 the calico, and then submitted to the action of steam, the Prussian blue 

 so produced being fixed on the cotton fibre b} r means of the oxide of 

 tin, resulting from the decomposition of the salt employed. 



Nothing is more simple than to gild or silver metals by means of 

 ferrocyanide of potassium, or to cover iron and other metals with copper. 

 To obtain a gilding liquor, it is only necessary to take 1,000 parts of 

 water, adding to it 100 parts of yellow prussiate of potash, 10 parts of 



