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Richard Brunquell passes ammonia through tubes filled with charcoal, and heated to redness so as to form cyanide of ammonium, which is converted into the ferrocyanide of potassium by contact with potash solution and suitable iron compounds.
He begins by forming the phantom, in the usual way, upon paper prepared with ferrocyanide, and exposes it to daylight for a sufficient length of time. The filings form a screen which is so much the more perfect in proportion as it is denser, and, after fixation, there is obtained a negative phantom, that is to say, one in which the parts where the field is densest have remained white.
Dyspnoea, depression, cold extremities, headache, purple line round the gums. Jaundice is common. A chronic form of poisoning may occur, with symptoms closely resembling those of lead. Post-Mortem Appearances. Inflammation of stomach and intestines, which are bluish or green in colour. Treatment. Encourage vomiting. Give albumin or very dilute solution of ferrocyanide of potassium.
The theory of the formation of this salt is, that one eq. of chlorine withdraws from two eq. of the ferrocyanide of potassium, one eq. of potassium, forming chloride of potassium, which remains in the mother liquid.
Thus, for example, all salts of iron, which contain iron in the state of ions, give similar reactions; but salts such as ferrocyanide of potassium, in which iron does not play the part of an ion, never give the characteristic reactions of iron.
As saliva contains ferrocyanide of potassium, out of which sulphuric acid generates prussic acid, the latter substance will always be obtained by the process adopted by Professor Aiken from any stomach which has in it the least particle of saliva. If, then, the professor did really get prussic acid, without doubt he manufactured it. Dr.
Ferrocyanide of Potassium K Cfy+3HO, or K C N Fe+3HO, is generally known by the name of yellow prussiate of potassa. It contains ferrocyanogen, a compound radical, consisting of 1 eq. of metallic iron and 3 eq. of the elements of cyanogen, and is designated by the symbol Cfy. Cyanide of potassium is generated in large quantities.
Polished steel put into a solution containing a copper salt receives a coating of metallic copper. Ammonia gives a whitish-blue precipitate, soluble in excess. Ferrocyanide of potassium gives a rich red-brown precipitate. Sulphuretted hydrogen gives a deep brown precipitate. The salts of zinc requiring notice are the sulphate and chloride.
The melted mass is afterward treated with hot water, which dissolves the cyanide and other salts, the cyanide being then quickly converted by the action of oxide of iron, formed during the operation of fusing, into ferrocyanide. The filtered solution is evaporated, crystallized, and recrystallized. The best temperature for making the solution is between 158 and 176 deg.
F. The conversion of the cyanide into the ferrocyanide is greatly facilitated by the presence of finely divided sulphuret of iron and caustic potash. Some years ago this salt was manufactured by a process which dispensed with the use of animal matter, the necessary nitrogen being obtained by a current of atmospheric air.
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