136 MANUAL OF MILK PRODUCTS 



used by creamery men, as the percentage of acid may then be 

 read directly from the burette. Many devices for testing the 

 acidity of milk are on the market, all tending to do away with 

 computation and giving the percentage of acid directly. One 

 of these is Publow's acidimeter (see p. 300). In this apparatus 

 an n/10 alkali solution is used and 9 grams of milk are tested. 

 Each cubic centimeter on the burette equals .1 per cent acid 

 and each 1/10 of a cubic centimeter equals .01 per cent acid. 

 In testing for acid one should always try to obtain the same 

 degree of color each time. This color should be permanent for 

 at least one minute. Great care should be taken not to run in 

 an excess of alkali. It will be much easier to detect the color 

 change if some water is added to the sample after it is measured 

 out before the alkali is added. 



TESTS FOR SOLIDS NOT FAT AND TOTAL SOLIDS IN MILK (Ross) 1 



The instrument used to measure the specific gravity of a 

 liquid is called a hydrometer, and there are many kinds of 

 specialized hydrometers. The hydrometer used to test the 

 density of milk is called a lactometer, and, for the most part, 

 only two kinds are used. One is the Quevenne (called Q. for 

 abbreviation) and the other is called the Ordinary, or New 

 York State Board of Health (commonly called the "B. of H." 

 lactometer) . 



The Quevenne lactometer has a long, narrow stem which is 

 extended into a hollow glass tube of much larger diameter 

 than the stem itself. At the lower end of the instrument is a 

 bulb of mercury which causes the lactometer to sink in the 

 liquid to its proper level. The upper part of the stem contains 

 a thermometer scale, as it is important to know the tempera- 

 ture of the milk when the lactometer reading is taken. This 

 scale does not record high temperature, and, therefore, the 



1 A Dairy Laboratory Guide, Orange Judd Co. 



