1835. J Poggendm-ff's Annalen der Physik, ^c. 387 



duced, but after standing for some time, or by boiling, a brown cry- 

 stalline substance falls in fine scales. After drying, the substance 

 forms a brownish yellow mass, which is soluble in ammonia, but not 

 in water or alcohol. When heated in a glass tube it becomes first ' 

 blue, then purple-red, and assumes a dark colour, but gives out no 

 water. By caustic alkalies it is resolved into hydrate of copper, and 

 ferro-cyanodide of ammonia ; and by acids into ferro-cyanodide of 

 copper, and ammoniacal salt. 



Dr. Bunsen found its comix)sition to be, iron 13*20, copper 30*33, 

 cyanogen 33*08, ammonia 16-14, water 2*25 =2, 4, 6, 4, 1, atoms 

 respectively. This composition may be expressed, considering the 

 ammonia as occupying the place of water, by 2 Pe Cy -f 2 Cu Cy -f 

 4 N H-i -f HO = 76- 125 the atomic weight. 



2. Ammonia Ferro-cyanodide of Zinc is prepared in the same 

 way as the preceding. It is a white crystalline powder. Analysis 

 afforded for its composition, iron 13*15, zinc 32*27, cyanogen 39'04. 

 ammonia 11-.50, water4*0=2FeCy + 2 Zn Cy + 3 NHa + 2 HO. 



3. Ammonia Ferro-cyanodide of Mercury. — The preparation of 

 this salt is attended with some difficulty ; because, ammonia nitrate 

 of mercury dissolves in nitrate of ammonia when excess of alkali is 

 present. When Ferro-cyanodide of potash is added to this solution, 

 a yellowish precipitate subsides, which, when the solution attains its 

 proper degree of dilution, settles on the sides of the glass, in the form 

 of small, transparent, shining, wine-yellow, four-sided prisms. But, in 

 order to obtain them, several precautions are necessary. The solution 

 must contain as little water as possible. The solution must not be too 

 much concentrated, nor must the precipitation be conducted by heat, 

 because part of the mercury will be reduced, and the product will 

 have a gray colour. It is best to discover the necessary degree of 

 concentration by some preliminary trials, — to precipitate the com- 

 pound in a vessel surrounded by ice, and then to agitate the solution. 

 A yellowish precipitate subsides, from which the supernatant liquor 

 is to be removed, and a quantity of concentrated ammonia poured 

 over it. As long as the salt is impregnated with ammonia it retains 

 a fine citron-yellow colour, and crystalline structure. By drying in 

 the open air it undergoes partial decomposition. When treated with 

 water it becomes red. It consists of iron 8*58, mercury 59*09, cyano- 

 gen 23*74, ammonia 5*19, water 3*40: expressed by Fe Cy -j- 2 Hg 

 Cy + NH3 4- HO. 



4. Ammonia Ferro-cyanodide of Magnesium is procured by 

 adding to a solution of a magnesia salt, ammonia, till no further pre- 

 cipitation takes place, and then pouring in a solution of ferro-cyano- 

 dide of potassium. After standing or boiling, a white powder falls. 

 It consists of iron 18*86, magnesium 10*72, ammonia 10*75, cyano- 

 gen 56*27, water 3*40 = 7 (Fe Cy + 2 Mg Cy) + 5 (Fe Cy + 2 

 NH3 Cy) + 6 HO. 



Another compound was formed by using ferro-cyanodide of calcium 

 instead of the salt of potash. The constituents were, iron 18*24, 

 magnesium 8*93, ammonia 11*43, cyanogen 53*91, water 7'49, 

 abstracting the lime which was found in it. This is equivalent to 

 (Fe Cy + 2 Mg Cy) + Fe Cy + NH^) _^- 2 HO. 



2c2 



