36 DAIRY LABORATORY GUIDE 



the viscosity add viscogen. The formula for vis- 

 cogen is 2J parts of sugar, or all that will dissolve 

 without caramalizing, 5 parts water, ^ part milk 

 of lime. Prepare one gallon. Mix thoroughly and 

 allow to stand for at least twenty-four hours. Vis- 

 cogen is an alkali and if too much be added it gives 

 a bad odor and bitter taste. One ounce of viscogen 

 is sufficient to restore the viscosity in five gallons of 

 sweet cream. The higher the per cent of acidity the 

 more it will require. Where viscogen is added to 

 cream for market it should be labeled visco-cream. 



EXERCISE XI 

 CREAM GRADING 



Make acid test; curd test; heat a sample of milk or 

 cream to 120 F., and note odor. Take lactometer 

 reading. First-grade cream should test between 30 

 and 50 per cent butter fat, from to .2 per cent 

 acid, and have a good clean flavor. Second-grade 

 cream may test from 20 to 50 per cent butter fat and 

 have not higher than .3 per cent acid, and fair flavor. 

 Third-grade cream should not be used for butter- 

 making. 



A test for ammonia in milk or cream may also be 

 made by adding 10 c.c. of 10 per cent solution of 

 bichloride of mercury and potassium iodide (Nessler's 

 Reagent) to 10 c.c. of milk. A precipitate is at once 

 thrown down. Filter and add 3 per cent solution of 

 pure milk of lime until a black precipitate is formed 

 which disappears with an excess of reagent. This 



