MERCURIC SALTS CHANGE INTO EACH OTHER. 



17 



that contact with acids must largely if not wholly reverse it. 



Dissociation of mercurous sulphate by heat. — Boiled for some hours 

 with water, in the same way as mercurous nitrate, mercurous 

 sulphate was found to be converted, to a small extent, into basic mer- 

 curic sulphate, mercury, and sulphuric acid. The mercury was got as 

 a sublimate, the water became acid, and the undissolved sulphate 

 yielded some mercuric chloride when treated with hydrochloric acid. 



Oxidation of mercurous sulphate at 150°. — Heated for six hours in 

 oxygen, with water and a little sulphuric acid, in a sealed tube at 

 150°, one gram of mercurous sulphate gave no mercury, but .0121 

 gram mercuric radical, indicating the oxidation of 1.5 per cent, of the 

 mercurous sulphate. It should, I think, be taken into account that 

 through insolubility much of the sulphate is kept out of contact with 

 the oxygen, and unacted upon, during the heating in the tube, and the 

 same is true of the phosphate and chloride. 



(Literature). — Planche's very old process of making calomel has 

 illustrated, for a long time, the union of mercury with mercuric sulphate 

 even before heat is applied. According to Kane, mercurous sulphate is 

 not convertible into basic salt by water. Rose observed the dissoci- 

 ation of mercurous sulphate by boiling it, for a long time, with much 

 water, but he did not get the mercury as a sublimate, as I have done, 

 but along with the basic mercuric sulphate and the unchanged mer- 

 curous sulphate. The mercury must have condensed in the upper part 

 of the vessel he used, and then rolled down. Proust and also Donovan 

 are said to have got a yellow residue by boiling mercurous sulphate 

 witli water, no mercury being mentioned. 



Mercury phosphates. 



Conversion of mercuric to mercurous phosphate. — Moist mercuric phos- 

 phate triturated with its equivalent of mercury unites with it, growing 



