2 BULLETIN 1114, U. S. DEPARTMENT OF AGRICULTURE. 
with the protein, giving rise to a yellow-colored compound, the 
shade of the color depending on the amount of iodin liberated. If, 
however, only small amounts of iodin were liberated, then the colored 
protein compound would be masked by the large excess of unaltered 
protein. The small amount of colored protein could then be made 
to react with starch, producing a blue color which could be more 
readily discerned, thus making the test more delicate. 
In order to determine in what dilution the hypochlorites and 
chloramins can be detected in milk and cream a series of solutions, 
each containing 100 cubic centimeters of milk or cream plus definite 
amounts of hypochlorite or chloramin solution, were prepared, so 
that the final results were solutions containing chlorin from 1:1,000 
to 1 : 100,000 parts of milk or cream. The flasks containing these 
solutions were placed in the ice box for 24 hours and then examined 
for chlorin. After standing at room temperature for several hours. 
the flasks were returned to the ice box. and again examined after 
4^ hours. A flask of plain milk was added as a control. 
PREPARATION OF REAGENTS. 
(a) Potassium iodid solution. — Dissolve 7 grams of potassium 
iodid in 100 cubic centimeters of distilled water. Prepare fresh. 
(b) Hydrochloric acid. — To 100 cubic centimeters of concentrated 
hydrochloric acid add 200 cubic centimeters of distilled water. 
(c) Star-cli .solution. — Boil 1 gram of starch in 100 cubic centi- 
meters of distilled water. Cool before using. 
THE TEST. 
(1) To 5 cubic centimeters of milk or cream in a medium-sized 
test tube add 1.5 cubic centimeters of the iodid solution, mix thor- 
oughly by shaking, and observe the color of the milk. 
(2) If unaltered, add 4 cubic centimeters of hydrochloric acid. 
mix thoroughly by means of a glass rod flattened at one end, and 
note the color of the curd. 
(3) Xext place the tubes in a large water bath, previously heated 
to 85° C, and allow to remain for 10 minutes. During this in- 
terval the curd will have risen to the surface. 
(4) The tubes are then cooled rapidly by placing in cold water, 
and when cold are examined for any color change that may have 
taken place, either in the curd or in the liquid below. 
(5) Finally, add 0.5 to 1 cubic centimeter of starch solution to 
the liquid below the curd and note the result. 
REACTION IN MILK. 
Milk containing 1 part of chlorin in 1,000 parts of milk acquires 
a distinct reddish color, while at 1:2.500 dilution it is still slightly 
