RECENT PROGRESS IN PHYSICS. 387 



which the precipitated metal was not determined, but the amount of 

 evolved chlorine ascertained by the loss of weight of the electrode, 

 which was of copper. In this manner experiments were made — 



With chloride of copper Cu. CI. 



chloride of iron Fco CI3. 



chloride of tin Sn CI2. 



chloride of antimony Sbg CI5. 



The chlorine computed as equivalent with the water agreed in all 

 these cases with that observed, though only one of the combinations, 

 viz, Cu CI, has equal constituents of the constituent parts. 



Iodides and Bromides gave similar results. 



Becquerel also instituted experiments with oxides. H^ dissolved 

 sub-oxide Cu^ and oxide of copper Cu 0, each separately, in liquid 

 ammonia, and closed the flask air-tight by means of a cork, through 

 which the wires of the electrodes passed. Simultaneously with either 

 of these solutions a solution of nitrate of copper, serving as a volta- 

 meter, was inserted into the circuit of a single constant zinc-copper ele- 

 ment. These experiments, each of which was continued for several 

 hours_, demonstrated that for 1 equivalent of copper, precipitated at 

 the negative pole of the voltameter, charged with nitrate of copper, 

 there were deposited — 



2 equivalents of copper from the solution of Cuj 0. 

 1 equivalent of copper from the solution of Cu 0. 



The last binary combination examined by Becquerel was oxygenated 

 water H O2. For every equivalent of water decomposed in the in- 

 serted voltameter two equivalents of oxygen were liberated from the 

 oxygenated water at the positive pole. 



The researches on the electrolysis of solutions of different salts lead 

 to results similar to those which we have seen were obtained by Daniell. 



Faraday's proposition, therefore, that binary combinations are only 

 electrolytes when they are composed of equal equivalents of both con- 

 stituent parts proves to be untenable, since many bodies can directly 

 be decomposed by the current which do not fulfil this condition. 



In reference to the quantity of decomposition, the result of Becque- 

 rel's researches may be best expressed in the words of Poggendorff : 

 that with an equal force of current for every equivalent of water there 

 is also an equivalent of any combination decomposed, provided that 

 it can be decomposed at all. 



§ 178. Formation of cldoride of nitrogen hy electrolysis. — When a 

 saturated solution of sal ammoniac, between platinum electrodes, is 

 exposed to the galvanic current hydrogen is evolved at the negative 

 pole, but no chlorine at the positive, and, if the solution is sufficiently 

 concentrated, no oxygen either, but the positive platinum plate be- 

 comes covered with small, yellowish, oily drops of chloride of nitrogen. 



When spirit of turpentine is poured upon the solution, the rising 

 drops detonate as soon as they come in contact with tlie turpentine. 

 It is better to place the ])ositive pole not vertically but in an inclined 

 position in the fluid. This interesting phenomenon was discovered 

 nearly at the same time, without the knowledge of each other, by 



