381 Occurrence of a compound of Acetylene in Copper Gas-pipes. 



ceeds, sulphuric acid becomes free, and the solution must be 

 saturated either by adding oxide of nickel or ammonia. In the 

 first case the solution always remains at the same degree of con- 

 centration ; in the latter a double sulphate of nickel and ammonia 

 is formed, which is scarcely soluble in water, but soluble in water 

 to which ammonia has been added. At the expiration of some 

 time a white brilliant deposit with a slight yellowish tinge is 

 obtained. It has also magnetic polarity like cobalt. 



Gold. — A neutral and very concentrated solution of chloride 

 of gold is rapidly decomposed even by a single element of weak 

 electromotive force, metallic gold being used for the positive 

 electrode. The metal becomes ductile by being annealed. Alka- 

 line solutions need not be added, but the intensity of the current 

 must be proportional to the density of the liquid. 



With solution of silver the result is the same : the solution 

 must be neutral, the current feeble, and a positive electrode is 

 indispensable. 



Platinum is more difficult to obtain as a coherent mass ; the 

 negative electrode must be of platinum, round which the metal 

 is often deposited in tubercles. 



M. Crova has made a communication* on the formation of 

 cupreous acetylene in copper gas-pipes. Copper gas-pipes which 

 have been long used as conduits fur coal-gas frequently give rise 

 to dangerous explosions while they are being cleaned out. M. 

 Crova has made it probable that this may arise from the pre- 

 sence of cupreous acetylene, which detonates at a high tempera- 

 ture or when struck. The author exposed a quantity of reduced 

 metallic copper in a flask containing a mixture in equal volumes 

 of air and acetylene, to which in one case a little ammonia was 

 added. The copper became black, and after the lapse of some 

 time the flask, on being opened under water, showed that about 

 one-half had been absorbed ; the absorption in the flask con- 

 taining ammonia was somewhat greater. The copper was washed 

 and dried ; on being treated with hydrochloric acid, a consider- 

 able quantity of acetylene was disengaged; when thrown on a 

 heated metallic plate, an explosion was produced, much more 

 violent than with pure cupreous acetylene. As coal-gas always 

 contains acetylene, some traces of air, and even of ammonia, the 

 formation of the acetylene compound can be readily understood. 



Pelouze and Cahourst have investigated some of the American 

 petroleum now so extensively used for illuminating and other 

 purposes. The greater part of the oil which they examined 

 boiled regularly at 68°, and formed a colourless and inodorous 



* Comples Rendus, September 8, 1862. 

 t Ibid. June 23, 1862. 



