"USE OF LIME WATER AS A STANDARD SOLUTION IN 

 TESTING THE ACIDITY OF MILK AND CREAM." 



It was observed as long ago as 1877 that acidity and ripe- 

 ness of cream bore a definite relation. The relation of sour- 

 ness of milk to its marketability is as old as the centuries, but 

 ip creating more* commercial attention since the discovery of 

 the necessity of using perfectly fresh milk for pasteurisation. 

 For thi;- purpose a test even more delicate than the sense of 

 taste is required. 



Fleischmann & Sebelien, in the old world, and Mann, in 

 America, introduced the chemical method of titrating cream 

 with standard alkali, using phenolphthalein for indicator. A 

 modification of the same method is in common use for testing 

 the acidity of milk. The alkalies almost universally used have 

 been deci-iiormal solutions of sodium or potassium hydrate. 

 Farrington has introduced the alkali in tablet form. 



Wallace, the Chr. Hansen Laboratory, and probably 

 others, have suggested lime water, and this alkali is now quite 

 generally used in Denmark and Sweden. 



According to Richmond, Storch uses a solution of lime 

 (limp water) containing solid lime, as it remains constant in 

 composition and is almost exactly twentieth normal. The 

 strength of the solution remains constant as if any of the lime 

 is removed by carbon di-oxide more is dissolved. Its strength 

 s but little affected by climatical variation of temperature. 



I am indebted to Mr. Monrad for the account of the fol- 

 lowing method of preparation which is probably that in use 

 in Denmark and Sweden. "The lime is dissolved in a bottle 

 carefully shaken and then left to settle again. In this way 

 is obtained a solution which, by a reasonably uniform tern 

 per? lure will keep unchanged for several months." 



Dr. E. Holm prepared two samples in this way which were 



E. Holm prepared two samples in this way which were 

 titrated from time to time at different temperatures and 

 showed quite close agreement. Only slight variation was 

 shown at different temperatures. Thus using 20 CC lime 

 water, one sample gave the following result: 



