384 EECENT PROGRESS IN PHYSICS. 



In the electrolysis of tlie monobasic salt, P Og goes to the positive 

 pole and forms the protohydrate H-}-P Og. 



§ 175. Electrolysis of arsenites and sulphites. — The English physi- 

 cists next directed their attention to the electrolysis of salts whose 

 acids had a lower degree of oxygenation than those already examined. 

 The negative cell was charged with a solution of arsenite of potassa, 

 (K 0+As O3,) the positive with a solution of potassa. At the positive 

 pole oxygen was evolved, but no hydrogen appeared at the negative 

 pole, the electrode being covered with metallic arsenic. According to 

 Daniell's view, K was liberated in the negative cell by electrolysis, 

 and by its oxydation enabled the corresponding H to reduce the arse- 

 nious acid ; As O4 was transferred to the positive cell, one equivalent of 

 oxygen liberated and the remaining arsenious acid formed with the 

 potassa present arsenite of potassa. 



Sulphite of potassa (K O+S O2) in both the cells gave hydrogen at 

 the negative, but no oxygen at the positive pole ; sulphuric acid was 

 produced in the positive cell, which by acting upon the sulphite evolved 

 some sulphurous acid, K was liberated by the current at one pole and 

 hydrogen evolved by its oxydation ; SO2+O, designated by Daniell 

 as Suboxysulphion, was transferred to the other and appeared there as 

 SO3. 



Hyposuljjhite of Soda (Na O-j-Sa O., gave similar results. Hydrogen 

 was evolved at the negative pole, and no gas at the positive pole, but 

 a strong smell of sulphurous acid was perceived there, accompanied by 

 a gradual deposit of sulphur. 83 OsH"^ passes to the positive pole, is 

 decomposed into S^SO^, and by the action of the sulphuric acid upon 

 the surrounding salt sulphurous acid is evolved. 



Tlie experiments on the electrolysis of the yellow and red prussiate 

 of potash we cannot discuss in this place. 



§ 176. IVans/er of the bases. — In the electrolysis of the phosphates 

 the acid was carried into the positive cell filled with a solution of Foda. 

 Daniell next endeavored, inversely, to transfer the bases of the i)Osi- 

 tive cell into the negative one filled with acid. With a solution of 

 sulphate of copper and potassa Cu 0. S O3+KO. S O3 only traces of 

 copper were carried to the negative cell and dej^osited at the negative 

 pole, but it was found that, compared with the gases evolved, ^ equiv. 

 of potassa had been transferred to the negative cell. 



A solution of sidphate of aluvmia and potassa (alum, Alo O3, 3 S O3 

 -f-KO.SO.) gave similar results; potassa was transferred to llie 

 negative cell in the same proportion as in the previous experiment, 

 but no alumina. 



From a solution of .ndphate of magnesia and potassa (Mg 0. S O3-I- 

 K 0. S O3) in like manner only potassa was carried over with a minute 

 quantity of magnesia. 



Instead of the double-salts a series of solutions of sesquisidphate of 

 alumina (Alg O3. 3 S O3,) of sesquisulphate of iron (FCg O3 3. S O3) and 

 sidphate of copper (Cu O. S O3) were next introduced into the positive 

 cell and the negative charged with diluted sulphuric acid. Neither 

 alumina nor oxide of iron or copper passed in perceptible quantities 

 into the negative cell. Both the cells were then filled with a solution 

 of sulphate of copper. The metal precipitated at the negative pole, 



