276 Prof. W. Beetz on the Development of 



positive aluminium wire to the ready solubility of the basic chlo- 

 ride of aluminium. This, though undoubtedly a true cause, 

 is not the sole one. It is to be presumed, from what has gone 

 before, that the development of hydrogen from the aluminium 

 and the magnesium has a common origin ; besides, the positive 

 aluminium wire also becomes black during electrolysis, and at 

 the end of the process continues to give off hydrogen, like the 

 magnesium wire, only not so abundantly. All the cases of elec- 

 trolysis examined by Wohler and Buff furnished a solution of 

 basic chloride of aluminium ; and it never occurred to them to 

 investigate cases of a different kind, their interest being concen- 

 trated on the formation of siliciuretted hydrogen. If in place 

 of a strong solution of chloride of sodium a dilute one be em- 

 ployed, the alumina is no longer completely soluble, and the ex- 

 periment then bears a greater resemblance to that with magne- 

 sium. The wire not only turns black, but the whole of the liquid 

 in the eudiometer becomes grey. A grey powder separates from 

 the wire, and continues to evolve hydrogen after the electrolysis 

 is interrupted. I have never seen it become entirely white. If 

 washed on a filter and treated with dilute hydrochloric acid, it 

 completely dissolves ; it contained no silicium, or only trifling 

 quantities, like the aluminium wire itself, which I obtained from 

 the same source as the magnesium wire used in the foregoing 

 experiments. The solution contained iron, however ; and to this 

 the grey colour may possibly have been due. The electrolysis 

 observed by Wohler and Buff with concentrated solution of chlo- 

 ride of sodium between aluminium wires corresponds therefore 

 entirely to that, examined by me, of solution of sulphate of mag- 

 nesium between magnesium electrodes; we ought consequently 

 to find also in the latter case the nearly constant ratio of H_ : H + . 

 The electrolysis of dilute solution of common salt no longer gave 

 this proportion ; on the contrary, I invariably found the alumi- 

 nium dissolved to be equivalent to two-thirds of the quantity of 

 hydrogen given off from the two poles. I believe, therefore, 

 that in the case of aluminium also the formation of a suboxide 

 precedes the evolution of hydrogen. A peculiar circumstance 

 prevents the separation of this suboxide. On account of the 

 solubility of the basic chloride, no great quantity of the substance 

 could be obtained either from dilute solution of chloride of sodium 

 or from dilute hydrochloric acid. In other salt solutions and in 

 dilute sulphuric acid, however, no evolution of hydrogen tal^es 

 place ; here, on the contrary, the phenomenon is that which has 

 been already described by Buff*. The positive aluminium wire 

 becomes covered with a dark incrustation, which is strongly 

 electro -negative and a very bad conductor; it gives off a little 

 * Ann. der Chem. und Pharm. vol. cii. p. 269. 



