MILK INSPECTION 217 



To 5 c.c. of the pasteurized product add 2 drops of a 2 per cent, 

 solution of paraphenylenediamin, and 1 drop of a 2 per cent, solution 

 •of hydrogen peroxide, and agitate. 



Not more than a tinge of blue shall be obtained by this test within 

 30 seconds after mixing. 



Rule 5. Butter. Butter shall respond to the following test : 



Twenty-five grams of pasteurized butter placed in a small beaker 

 and heated by being placed in water at 60 degrees centigrade, the clear 

 butter fat then poured off and the remaining liquid then diluted with 

 an equal volume of water. The mixture thus obtained is now treated 

 with 2 drops of a 2 per cent, solution of paraphenylenediamin and one 

 drop of a solution of 2 per cent, hydrogen peroxide. 



When thus treated not more than a perceptible blue color shall be 

 obtained within 30 seconds after mixing. 



Rule 6. Pasteurizing temperatures. All pasteurized milk, cream, 

 skimmed milk, milk products, and milk and cream used in the produc- 

 tion of milk products shall be pasteurized in accordance with the follow- 

 ing regulations : 



(a) Continuous pasteurization — In all continuous pasteurization, 

 the milk and cream shall be heated to a temperature which shall be 

 determined and fixed by the department of health for each machine 

 at a point corresponding to the temperature required to kill 99 per cent, 

 ■of the bacteria and all pathogenic bacteria contained in the raw pro- 

 duct. For this determination, ordinary raw milk containing in the 

 neighborhood of 3,000,000 bacteria shall be used and the pasteurized 

 product shall be collected as it flows from the cooling apparatus. 



All continuous pasteurizers shall be equipped with a feeding pipe 

 which is so constructed that the pasteurizer cannot be fed in excess 

 of its normal working capacity ; that is, in excess of the working cap- 

 acity of the machine at which 99 per cent, of the bacteria are killed 

 when the required amount of heat is applied. 



All continuous pasteurizers operated outside the city limits, for 

 the production of pasteurized milk and milk products to be sold at the 

 city of Chicago, shall be equipped with an apparatus regulating auto- 



