96 
Equine Piro2)lasinosi.s 
It is necessary to know how much oxygen corresponds to a difierence of pressure of 
1 mm. on the scale. For this purpose a known volume of oxygen is liberated in the 
apparatus (about 0-2 c.c.). An experiment similar to that described, but with different 
fluids, is performed. The blood is replaced by hydrogen peroxide, the ammonia by water 
and the ferricyanide by potassium permanganate (approximately 1 c.c. = 0-003 g. perman¬ 
ganate). The hydrogen peroxide must first be carefully standardised by titration with 
standard potassium permanganate in the presence of sulphuric acid with which reagent it 
gives off its oxygen as follows : 
K.,Mno08 + 5H„0., - = K^SO^ -r 2MnSOj -t- 5HoO -i- 50„. 
In the apparatus itself it is better to dispense with the sulphuric acid. The relation of 
316 grams of permanganate to 1110-00 c.c. of oxygen remains true. 
