1819.] formed of Sulphur and Oxygen. 35& 



the quantity of sulphur in each of these groups is different, and 

 we cannot express their composition in terms of the same series* 

 The salts of each group have likewise a much greater relation to 

 each other than to those of the other group. 



The following; table exhibits the composition of the different 

 acid compounds of sulphur and oxygen : 



Hyposulphurous acid 2 prop, sulphur and 2 prop, oxygen 



Hyposulphuric acid 2 5 



Sulphurous acid 1 2 



Sulphuric acid 1 3 



Or if we prefer to consider the quantity of sulphur in each acid 

 as constant, the oxygen combines with it in the following pro- 

 portions : 



Let us now return to the properties of the nyposulphates. If 

 Ave pour upon one of these salts sulphuric acid, so much diluted 

 that.it will produce but little heat, we perceive uo particular 

 phenomenon ; but if we heat the mixture, or if the sulphuric acid 

 be concentrated, sulphurous acid is immediately disengaged.. 

 This result is easily understood. At a low temperature, the 

 hyposulphuric acid preserves its permanence ; but as has been 

 observed already, it is decomposed into sulphurous and sulphuric 

 acids at a temperature somewhat elevated. The solutions of the 

 hyposulphates do not alter, or at any rate alter very slowly, 

 when exposed to the air. 



Hyposulphate of potash crystallizes in cylindroidal prisma 

 terminated by a plane perpendicular to their axis. 



Hyposulphate of lime forms regular hexahedral plates grouped 

 usually in roses. 



The crystals of hyposulphate of strontian are very small. They 

 appeared to us to have the form of six-sided plates, whose edges 

 are alternately inclined contraryways, similar to those which 

 would be formed in an octahedron by sections parallel to two of 

 its opposite faces. 



Hyposulphate of manganese is very soluble, and even deli- 

 quescent. We may take advantage of this property to separate 

 it from the sulphate formed at the same time with it, when per- 

 oxide of manganese is dissolved in sulphurous acid. In this way 

 of proceeding, we lose a much smaller quantity of barytes for 

 saturating the solution. It is true that for this object we may 

 employ various other bases. 



The formation of sulphate of manganese iii the circumstances 

 just mentioned, appeared to us to deserve a particular examina- 

 tion ; but we have hitherto been able to make only a few imper- 

 fect experiments. From the composition of hyposulphuric acid 

 and of peroxide of manganese, it would appear that we ought to 

 obtain either neutral hyposulphate of manganese, or sulphate. 



' Z 2 



