RECENT PROGRESS IN PHYSICS. AOd 



ler's Journal of 1845 and 1846. So far they have had little or no 

 practical success. 



The idea of precipitating alloys, mentioned in the report of the 

 academy, though it there is represented as already confirmed by 

 experiment, was afterwards carried out by Von Ruolz. He actually 

 succeeded in depositing bronze upon iron, specimens of which lie pre- 

 sented to the academy, but found that the proportion of the metals 

 in the solutions should be different from that in the alloys required. 

 Von Piuolz dissolved, in 500 parts of water, a sufficient quantity of 

 cyanide of potassium to produce a solution of 4° Beaume, and added, 

 at a temperature of 40° — 48"' R., first, 30 parts of cyanide of copper 

 and then 10 of oxide of tin ; from this deposits with 10 to 20 per cent, 

 of tin were obtained. Afterwards Jacobi also took up this subject 

 (Dingler's Journal, vol. 93, from Bulletin de St. Petersbourg) and 

 prepared a brass solution by using, in a solution of cyanide of potas- 

 sium, an anode of copper and a kathode of platinum, until the latter 

 became covered with copper ; he then used an anode of zinc until the 

 precipitate assumed the desired color ; after this he was able, by using 

 an anode of brass, to coat iron with brass. Although I made many 

 trials I could never succeed in precipitating brass in this manner, the 

 color of the deposit soon changed and the brass anode became black; 

 from some remarks it seems that Jacobi had a similar experience. 

 But I have obtained strong and adherent coatings of brass upon iron 

 by using, instead of a brass anode, one of copper and zinc together, 

 each of which metals could be immersed to a greater or less depth, 

 until the desired color was obtained. This is in accordance with the 

 experience of Von Ruolz. 



That gold can be precipitated, alloyed with copper, has already been 

 mentioned ; but it is considered better to deposit at first a layer of 

 pure gold before adding ihe cyanide of copper to the solution of gold. 



When the metallic solutions become exhausted by use, either the 

 force of the current has to be increased or some of tlie concentrated 

 solution must be added. But at present the anodes are usually made 

 of the metal to be precipitated, and by these the solution is kept at 

 the required state of concentration ; formerly the anodes Avere always 

 made of platinum. This expedient has already been mentioned by 

 Petzhold, in his memoir, "Die galvanische Vergoldung, Versilberung 

 und Verkupferung, Dresden uud Leipzig, 1842 ;" and Jacobi, in his 

 treatise on coating with brass, remarks that it is not at all necessary 

 to make metallic solutions in a chemical way ; that the solution may 

 be obtained by using, in a solution of cyanide of potassium, an anode 

 of the required metal and kathode of platinum, until the metal de- 

 posits upon the latter. Such anodes are made of tliinly rolled sheets 

 of the metal soldered to a platinum wire. In silvering, anodes of 

 silver are only applicable with strong currents, or cyanide of i)otas- 

 sium in excess ; because, according to Napier, (Dingler's Journal, 

 vol. 95, from Philosophical Magazine, November, l!S4i,) cyanide of 

 silver is formed which is insoluble in water, as well as in neutral 

 cyanide of" silver and })otassium. According to Napier's researches, 

 the cyanide of potassium is not decomposed while silver is in the 

 solution. 



