HYPOCHLORITES AXD CHLORAMINS IN MILK AND CEEAM. 3 



discolored when compared with the control. This holds good for 

 both hypochlorites and chloramins. 



In case the milk contains an amount of hypochlorite corresponding 

 approximately to 1 part of chlorin in 5,000 parts of milk, then the 

 milk acquires a pale-yellow color on the addition of the iodid solu- 

 tion, and the color deepens as the amount of chlorin increases, so that 

 at 1 : 1,000 dilution the milk has a yellowish-brown color. At 1 : 5,000 

 dilution the yellow color is not permanent and fades gi"adually. If 

 kept at room temperature it is necessary to add hydrochloric acid 

 at 1 : 5,000 dilution in order to bring out the yellow color. With 

 chloramins a yellow color is produced at 1 : 2.500 dilution. If less 

 chlorin is present than mentioned above, the milk retains its natural 

 color. 



In more dilute solutions of hypochlorites and chloramins it is 

 necessary to heat the milk-iodin-hydrochloric-acid mixture in order 

 to bring about the reaction. The cooling is necessary to prevent a too 

 rapid decomposition of the iodid by the excess of hydrochloric acid. 



With hypochlorites and chloramins the curd and the solution 

 below acquire a distinct pale-yellow color with 1 part of chlorin in 

 50,000 parts of milk. The shade of the color varies somewhat and is 

 a little paler with chloramins than with hypochlorites. The liquid 

 below the curd is also colored yellow, the shade corresponding to the 

 depth of color of the curd. 



When milk which has stood at room temperature for 24 hours is 

 treated as above, the coloration produced is a little paler than when 

 kept at ice-box temperature. 



The curd of the control which has been kept at ice-box temperature 

 shows only a slight yellowish tinge when compared with the curd 

 of a blank which contains no iodid. The liquid below the curd in the 

 control, however, is most distinctive, since it shows no trace of yel- 

 low when compared with the blank containing no iodid. 



The addition of starch to the liquid below the curd brings out the 

 reaction somewhat more prominently by changing the pale-yellow 

 color to a light-reddish purple, the coloration passing through red 

 purple into a deep-blue purple as the amount of the chlorin present 

 increases. The control is also slightly discolored by the addition of 

 starch and may acquire a light-straw color, but without any trace of 

 a red-purple tint. 



In milk which has been kept at room temperature for a long time, 

 the control may have a stronger straw color, but without any trace of 

 purple. On this account it is best to judge the presence of small 

 amounts of hypochlorites and chloramins by the color of both the 

 curd and the liquid below. 



