1 MILK 27 



2 hours the solid impurities in the milk have sunk downwards 

 and collected on the bottom of the test-tube. With the aid of 

 a clip the rubber connection between the bottle and the test- 

 tube is closed, the latter freed, and the majority of the milk 

 carefully removed with a pipette. Distilled water is then 

 filled into the test-tube, and, after well shaking, the contents 

 of the tube are poured on to a dry weighed filter, and the 

 residue washed with water until no trace of opalescence is to 

 be seen in the filtrate. The solid matter on the filter is then 

 washed repeatedly with alcohol and ether, dried and weighed. 



Very good and rapid results were obtained by Ballo l by 

 filtering the rnilk, without previous sedimentation, through 

 filters of very fine gauze made like ordinary filters. The gauze 

 should be of the finest, No. 18 or 20 (Dufour), and this will 

 retain all the particles which are visible to the eye but will 

 permit the largest fat globules to pass through. These gauze 

 niters are placed in a ribbed funnel, moistened with water, and 

 the rnilk poured in. This quickly passes through, leaving the 

 dirt, which can be further treated, as in Renk's method, by 

 washing with water, alcohol, and ether, and then weighing. 

 The above methods, with unimportant modifications, are those 

 generally employed in a determination of the dirt in milk ; they 

 are slow, but up to the present a rapid quantitative method is 

 not known. Instead of washing with pure water, Rosengren 

 recommends the addition of HC1, for otherwise there is danger 

 of the calcium phosphate, which is a normal constituent of milk, 

 being deposited in the dirt, and so the weight of the latter 

 would be too high. The calcium phosphate and similar 

 compounds are soluble in water containing HC1. 



Some of the more important modifications of Renk's method 

 may fitly find a place here. Bersch advocates the addition of 

 formalin to the milk, so that it does not quickly turn sour, and 

 the time of sedimentation can then be lengthened to 24 hours. 

 Winkler would like to employ 8-10 litres of milk instead of 

 1 litre. This certainly would be of advantage in many cases, 

 for the amount of dirt from 1 litre of cleanly-handled milk is 

 often minute and difficult to work with. 



Gerber has brought out a modification of Stutzer's apparatus 

 (p. 26), in which the bottom of the bottle is removed and the 

 1 Milch- Zeitung, 1904, p. 229. 



