and on a New Means of investigating them. 481 



J„J . HChH . O . S0 3 . HChH . O . So 2 . HChH . O . 

 S0 2 . . HChH . JJ 2 . 



It appears, however, that the sulphuric acid may be removed 

 not only by barium carbonate but by its hydrate, without 

 breaking up the molecule. It is easily shown that the solution 

 of herapathite after treatment even with barium carbonate 

 contains no sulphuric acid. This may be proved by adding to 

 the solution after the treatment, ammonia till it becomes pale 

 yellow, evaporating to dryness and then warming with very 

 dilute hydrochloric acid. An aqueous solution of barium 

 chloride then gives no precipitate, nor even any troubling by 

 standing. It seems perhaps doubtful if a substance having 

 the constitution indicated by the rational formula above cited 

 could have its molecule subsist unbroken, after the removal of 

 the sulphuric acid. 



The application of this test leads to the following conclu- 

 sions : 



1. Sulphates of the type J£' 2 SO i or Itf'SO^ 



I find that these salts dissolve in water and exist in solution 

 as such and absolutely without separation of sulphuric acid 

 even in those cases in which the solution is acid to litmus. 

 The substances examined were the alkaline sulphates and the 

 sulphates of Mg, Zn, Cd, Cu, Ni, Co, Mn, Tl, also the sulphates 

 of morphia, quinia, strychnia and brucia. To this series of 

 reactions there is a single exception of an interesting character. 



A solution of ferrous sulphate invariably contains free acid, 

 no matter how often recrystallized or under what circumstances 

 prepared. A small flask was filled with freshly distilled water 

 and was well boiled, corked and set aside to cool. In this, 

 ferrous sulphate was dissolved and potash was added in quan- 

 tity sufficient to precipitate a considerable proportion of oxide. 

 Even this solution gave the reaction indicating the presence of 

 free acid. So too the double salts of ferrous oxide with 

 ammonia and with magnesia, their solutions always contain 

 free acid, no matter how often they may be recrystallized or 

 purified by precipitation of their solutions in water by alcohol. 

 This exceptional behavior probably results from the great 

 tendency of ferrous solutions to rapid absorption of oxygen 

 from the air, and as will presently appear, sesquisulphates are 

 dissociated in solution. 



With this one exception the heavy metallic sulphates above 

 mentioned dissolve in water without decomposition although 

 their solutions redden litmus. The alkaloids mentioned yield 

 sulphates which after suitable purification are perfectly neutral 

 to litmus. 



