272 



Prof. W. Beetz on the Development of 



nesium electrodes (the negative plate can be replaced by a pla- 

 tinum electrode), a considerable quantity of black matter at once 

 deposits on the positive pole. Fart of this substance is swept 

 off by the current of gas, part falls to the bottom. A gas is con- 

 tinually being developed from this substance, even when it is no 

 longer in contact with the plate on which it was deposited. 

 Collected in a eudiometer and analyzed, the gas proved to be 

 hydrogen. If during the electrolysis the eudiometer be held 

 firmly upon its caoutchouc plate so that none of the black 

 matter can fall out, the current of course not being stopped, 

 and if, lastly, the measuring of the gas-volumes, when the current 

 has ceased, be delayed till there is no longer any gas disengaged 

 from the precipitate, it is then found that the sum of the volumes 

 of hydrogen evolved from the two poles is again equivalent to 

 the magnesium dissolved; the ratio of the two gas-volumes, 

 however, depends on the strength of the current. 



In the two following experiments dilute solution of chloride 

 of sodium was decomposed in the usual manner ; in experiment 

 8 six Grove's cells were used, and in experiment 9 the magne- 

 sium wire which was to form the positive pole was directly fast- 

 ened to the platinum wire as negative metal. 



No. 



H-. 



H+. 



1H-. 



M* 



Equiv. 

 II _. 



Equiv. 

 H + . 



Total. 



Loss. 



8 

 9 



14-9 



3-78 



100 



10-8 



4-96 

 1-26 



0016 

 0004 



0-011 

 00116 



0-027 

 0-0156 



0027 

 0017 



The ratio of H_ to H + was likewise never more than 3 to 

 1 when solution of chloride of ammonium was employed as elec- 

 trolyte. 



10 | 14-4 | 9-77 | 4-8 | 00154 | ; 0-0104 | 0-0258 | 026 



In this case no black precipitate was formed. 



If the black body produced by the electrolysis of a solution 

 of chloride of sodium be allowed to remain in the liquid, it is 

 soon covered with white flakes, and is finally converted into a 

 white muddy substance. This consists of hydrate of magnesia. 

 If the liquid be greatly diluted before this change is complete, 

 the black body can be perfectly purified by stirring the solution 

 briskly and pouring off the lighter white flakes. It undergoes 

 but little change in water ; by no method, however, have I 

 succeeded in drying it unchanged : when under the receiver of 

 the air-pump over sulphuric acid, as soon as it was nearly dry, 

 it became grey, and a mixture of white and black particles could 



