192 



CLEAN MILK 



evaporating dish or test-tube. (3) To this add one drop of art. 

 alcoholic solution of phenolphthalein (1 gm. to 7>° c. c. alcohol).. 

 (4). With another 1 c. c. pipette add drop by drop clear lime-water,, 

 and shake the tube to mix thoroughly, until the milk is colored a. 

 faint pink. Now note how many c. c. of lime-water were used. 



c.c. milk and phenolphthalein colored by o. 



1 c.c. lime-water .045 p. c. acid- 



•09 



.135 



.180 



.225 



.270 



•315 

 .360 



■40S 

 ■450 

 ■495 

 •540 

 •58s 

 .630 



•675 



A simple rule is : Multiply 0.0045, the weight in grams of 

 lactic acid neutralized by 1 c. c. lime-water, by the number of cubic- 

 centimeters of lime-water used, and divide by 100, which gives the 

 percentage of acidity. 



Cream Thickeners. — Viscogen, a solution of sugar, lime and 

 water, is commonly used to thicken cream. This adulteration can 

 only be determined by a chemist, making an exact analysis for 

 sugar and estimating the percentage of lime. Gelatine is sometimes, 

 employed as a thickening agent. This can be detected by adding, 

 to about 10 or 15 cubic centimeters of milk, twice the volume of 

 water and 10 cubic centimeters of acid mercuric nitrate solution 

 (10%). Shake the mixture vigorously and allow it to stand 

 a few minutes and filter. If much gelatine is present it is im- 

 possible to filter a clear fluid. To verify a suspicion of gelatine, 

 add to a small amount of the filtered fluid' an equal volume of a 

 saturated aqueous solution of picric acid. If any gelatine is present,.. 

 a yellow cloudiness will appear in the fluid. 



