118 M. Thenard oh Oxygenated Water. 



derable portion of manganese, become so hot as to bum the 

 hand. 



7. The fluid which now contains only hydro-chloric acid, water, 

 and oxygen, is placed in the glass it was first prepared in, and 

 its temperature lowered by ice, as before. Then, stirring it con- 

 tinually, sulphate of silver, prepared by dissolving oxide of silver 

 in sulphuric acid, is to be added, by small quantities at a time ; 

 and it is essential that the sulphate contains no free oxide. The 

 sulphate is decomposed by the hydro-chloric acid, and there re- 

 sults water, chloride of silver which precipitates, and sulphuric 

 acid in place of the hydro-chloric. When the quantity of sul- 

 phate of silver added is sufficient to decompose perfectly all the 

 hydro-chloric acid, the fluid suddenly becomes clear ; until that 

 is the case, it remains turbid. As it is required that no hydro- 

 chloric acid should remain, so also no excess of sulphate of silver 

 should be present ; and, therefore, the fluid must be tested suc- 

 cessively by nitrate of silver and muriatic acid, very small quan- 

 tities of the fluid being used for this purpose. 



When the proportions are well adjusted, the fluid is to be 

 passed through a filter, and the filter, after being allowed to 

 drain, is to be compressed in a cloth. The fluid obtained by the 

 compression, must be again passed through a filter, in conse- 

 quence of a slight degree of turbidness. 



8. The object of the preceding operations has been to obtain 

 a fluid composed of water, oxygen, and sulphuric acid. But 

 this acid must be separated ; for this purpose the fluid is put 

 into a glass mortar, surrounded by ice, and slaked barytes, very 

 pure and finely powdered, is to be added by small portions at a 

 time ; it is to be rubbed again in the glass mortar, and when it 

 is all united to the acid a fresh portion is to be added. When 

 the fluid scarcely reddens litmus paper it is to be filtered, and 

 the filter compressed in a cloth ; then after having united the 

 two fluids they are to be stirred, and the saturation of the acid 

 completed by barytes water. There must even be a slight ex- 

 cess of barytes water added to separate all traces of iron ; and, 

 above all, of manganese, which the fluid may still contain ; and 

 it is of importance to remember, that it must be filtered imme- 



