M. Thehard on Oxygenated Watei-. 117 



fluid with 125 times its volume of oxygen, but I added acid 

 enough to dissolve 30 grammes (463 grains) of the deut-oxide, 

 being careful also to preserve the acidity such, that at the end of 

 the operation I could dissolve about 20 grammes (309 grains) of 

 the deut-oxide, without the aid of sulphuric acid ; but I have 

 ascertained that, when the fluid contains nearly 50 volumes of 

 oxygen, it allows so much gas to escape from one day to the 

 next, that there is no advantage in continuing to oxygenate it by 

 the deut-oxide. 



5. When the fluid is oxyginated up to the required point, it is 

 to be saturated with deut-oxide, retaining it at the same time in 

 ice. Abundant flocculi of silex and alumine soon separate from 

 it, which are generally coloured yellowish-brown, by a little of 

 the oxides of iron and manganese. The whole should then be 

 thrown quickly on a cloth, enclosed in it, and strongly com- 

 pressed. This operation cannot be done well except by two 

 persons, and should be performed rapidly ; for though there is 

 but a very minute quantity of oxide of manganese, it is sufficient 

 to produce a considerable disengagement of oxygen, 



6. As the fluid which has passed the cloth may still retain a 

 small quantity of sdex, iron, and manganese : and as it is neces- 

 sary to separate all these substances, it is again to be surrounded 

 by ice, and barytes water added to it, drop by drop, the whole 

 being stirred. If, when the barytes is in such excess as to be 

 slightly sensible to coloured paper, there is no precipitate, it 

 proves that all the oxide of iron and manganese are separated ; if 

 they have not been completely separated in the preceding ope- 

 ration, they will by this. 



Immediately on the separation of them, the fluid must be 

 placed in two or three filters; for the oxide of manganese disen- 

 gages so much gas, that it cannot be removed too quickly. 

 Sometimes double filters arc required, because the gas sepa- 

 rating the paper, tears those that are single. Sometimes also, 

 to avoid losses, the small quantities which remain in the filters 

 first used, must be placed on fresh filters. Afterwards all the 

 filters should be compressed in a cloth, to separate the water 

 from them. Those which contain a comparatively consi- 



