Testing the Acidity of Milk and Cream. 113 



or cream by the so-called Manns' test include 

 one gallon one-tenth normal alkali solution; 

 four ounces of an alcoholic solution of phe- 

 nolphtalein, one 50 cc. glass burette with 

 stop-cock, one burette stand, and a pipette 

 for measuring the sample. This outfit will 

 make about 100 tests and is sold for $5.00. 



132. The Alkaline tablet test. Solid alka- 

 line tablets were proposed by Farrington in 

 1894, as a substitute for the liquid used in 

 Manns' test. 2 It is found possi- 

 ble to mix a solid alkali and 

 coloring matter, and compress 

 the mixture into a small tablet, 



FIG. 40. Apparatus used in 



which would contain an exact Manns' test. 



amount of alkali. The advantage of the tablets lies in 

 the fact that they will keep far better than a standard 

 alkali solution, and they can be easily and safely sent 

 by mail; they also require less apparatus and are con- 

 siderably cheaper than standard alkali solutions; 1,000 

 of these tablets, costing $2.00, will make about 400 tests. 3 

 Similar alkaline tablets were placed on the market in 

 Europe at about the same time, viz., Stokes' Acidity Pellets 

 in 1893, andEichler'stfaim^itoi (acid-pills) in 1895. * 



Two methods of using the tablets have been proposed, 

 one, for the titration (determination of acidity) of ripen. 



1 Devarda's acidimeter (Milchzeitung, 1896, p. 785) is built on the same 

 principle as Manns' test; one-tenth soda solution is added to 100 cc. of milk 

 in a glass-stoppered graduated flask, 2 cc. of a 4 per cent, phenol phtalein 

 solution being used as an indicator. The graduations on the neck of the 

 flask give the "degrees acidity" directly. 



2 Illinois experiment station, bulletin No. 32. 



3 The tablets are sold by dealers in dairy supplies. 



4 Milchzeitung, 1895, pp. 513-16. 



8 



