288 
cL 
Fia. 40.— Gerber-Lobeck 
catalaseapparatus. 1. Bottle 
with perforationin neck at a. 
2. Volumeter,showing (a) the 
middle tube, with scale; (b) 
the inner tube, through which 
the oxygen ascends from the 
bottle to the top of the middle 
tube, and (c) the openings 
through which the water es- 
capes from the middle to the 
outer tube. In the illustra- 
tion, oxygen collected at the 
top of the middle tube has 
depressed the water to the 3 
c.c. mark and elevated it a 
corresponding degree in the 
outer tube. (Courtesy Cor- 
nell Veterinarian.) 
Example: 
PRINCIPLES AND PRACTICE OF MILK HYGIENE 
diluted with twice the quantity of 
water to prepare a 1 per cent. solu- 
tion. Distilled water or well-boiled 
and filtered water should be used. 
For example: 100 c.c. hydrogen per- 
oxide, 200 c.c. distilled water. The 
solution should be standardized by 
titration with a tenth-normal potas- 
sium permanganate solution, as 
follows: 
Ten c.c. of the hydrogen peroxide 
solution is mixed with 90 c.c. of dis- 
tilled or boiled water. Of this solu- 
tion, 10 c.c. is placed in a beaker 
with 10 c.c. of dilute sulphuric acid. 
The dilute sulphuric acid is prepared 
by adding 400 c.c. of distilled water 
to 100 c.c. of sulphuric acid with a 
specific gravity of 1.82 to 1.825. 
About 5 c.c. of the tenth-normal solu- 
tion of potassium permanganate is run 
into the beaker from a burette and it 
is then added slowly until the solution 
takes on a pale violet color which 
remains after stirring. About 6 c.c. 
will be required for a 1 per cent. solu- 
tion of hydrogen peroxide. Each 
c.c. of the tenth-normal potassium 
permanganate solution is equal to 
0.0017008 gram hydrogen peroxide. 
0.0017008 K 6==0.0102048 XK 100 = 1.02 
per cent. hydrogen peroxide. 
The hydrogen peroxide solution should be kept in an 
