198 PROTEINS AND CARBOHYDRATES 
state that lipase is not widely distributed in the bactcilat world or, 
at least, this subject is little or almost not at all treated. Raneidity in 
butter has been attributed by some to the formation of butyric acid 
(Duclaux, 1887). Others maintain that the fat in butter is not attacked, 
Reinmann (1900) tried the effect of pure cultures on sterile butter and 
found that most bacteria did not attack fat. In cheese Laxa (1902) 
demonstrated that Ps. fluorescens decomposed fat quite extensively. 
Two other peptonizing bacteria and a yeast were also found which de- 
composed fat. Rahn (1905) stated that Penzcillium glaucum and a few 
bacteria possessed strong fat-splitting properties. Kendall and Simonds 
(1914) found that sterile filtrates of plain and dextrose broth cultures of 
B. typhi liberated acid from ethyl butyrate. This was also demon- 
strated in connection with acid-fast bacteria. 
Determination of the Iodine Absorption Number (Hanus Method.) 
The unsaturated fatty acids will react with the halogens. The amount 
of iodine differs according to the fat, and consequently this iodine 
absorption number is of some value for identification of fats. Iv 
(Iodine number) may be defined as the number of grams of iodine 
absorbed by 100 gms. of fat. 
Reagents. Hanus Iodine Solution. Dissolve 13.2 gms. of iodine 
in 1000 c.ec. of glacial acetic acid (99.5 per cent) showing no reduction 
with bichromate and sulphuric acid. Add 3 ¢c.c. of bromine to the cold 
solution. 
Starch Paste. Boil a gram of starch in 200 c.c. of distilled water for 
ten minutes and cool. 
Sodium Thiosulphate. Standardize a N/10 solution. 
Procedure. Weigh about 0.5 gm. of fat into a 250-c.c. glass-stoppered 
bottle and dissolve by adding 10 c.c. of chloroform. After solution add 
30 c.c. of the iodine monobromide solution. Place the bottle in the 
dark and allow to stand for thirty minutes. The time factor is impor- 
tant. The excess of iodine should be at least as much as is absorbed. 
One or two blanks should be made under identical conditions. If the 
first addition of iodine is used up, another addition should be made. 
Add 10 c.c. of potassium iodide solution and shake after which add 100 
c.c. of distilled water washing any iodine on the stopper of the bottle 
and sides back into the bottle. Titrate the iodine with the N/10 
sodium thiosulphate to a yellow color. Then add a few drops of the 
starch solution and continue the addition of sodium thiosulphate until 
the blue color has disappeared. ‘Toward the end of the reaction stopper 
the bottle and shake vidlently so that any iodine remaining in the 
chloroform may be taken up by the potassium iodide solution. The 
