254 MM. Laspeyres and Engelbach on Casia and Rubidia. 



Hydrochloric acid has hitherto resisted all attempts to decom- 

 pose it ; and the reason is not difficult to explain ; the tension 

 of dissociation at high temperatures is very small, and the ten- 

 dency to unite so powerful that it is not easy to see how the 

 momentarily separated substances cannot but reunite. But by 

 the following device Deville has succeeded in showing that there 

 is a slight dissociation. The silver tube in the above experiment 

 is amalgamated with a very thin coating of mercury, which is 

 not attacked by hydrochloric acid gas at a temperature of 300°. 

 Pure hydrochloric acid gas was admitted into the above appa- 

 ratus, a difference in temperature of about 1500° being main- 

 tained between the porcelain tube and the amalgamated silver. 

 At the close of the experiment, on moistening the tube with am- 

 monia, some of it was blackened, and a small portion of chloride 

 of silver dissolved. The gas, carefully collected, was found to 

 contain a distinct quantity of hydrogen. 



In a repetition of the carbonic oxide experiment, Deville found 

 that when some purified lampblack was placed in the apparatus 

 and heated to nearly the fusing-point of silver, and carbonic oxide 

 passed through, a considerable proportion of carbonic acid was 

 even then formed. 



By passing the electrical spark of a RuhmkorfFs coil through 

 carbonic oxide placed in a eudiometer containing some caustic 

 potash, it was completely decomposed into carbon and carbonic 

 acid, which was absorbed by the potash. For complete decom- 

 position, however, five or six days were required. 



Carbonic acid is decomposed by the electric spark into car- 

 bonic oxide and oxygen ; and if some phosphorus be placed in 

 the eudiometer so as to absorb the latter, the decomposition is 

 nearly complete in the course of twenty-four hours. 



Laspeyres* gives a complete account of the various substances 

 in which, up to the present time, the new alkaline metals caesium 

 and rubidium have been found, whether separately or together. 

 He also describes the occurrence of these two metals in a plu- 

 tonic silicate in the Rhine province. According to his ana- 

 lyses, the rock appears to contain about 0*00038 per cent, of 

 csesia and about 0'0003 per cent, of rubidia. He is still engaged 

 on the investigation of the occurrence of these minerals in rocks 

 of this origin. 



Engelbach has examined t a basalt from Upper Hesse, and 

 has found that it contains rubidium, apparently in larger quan- 

 tity than was found by Laspeyres. The rock contained no 

 csesium, but traces of the other comparatively rare substances, 

 titanium, chromium, and vanadium. 



* Liebig's Annalen, June 1865. f Ibid. July 1865. 



