i MILK in 



the fraction of a drop of water in the contents of a beaker at 

 once lowers the refractive index. The prism of the immersion 

 refractometer should also be suspended in the bath, so that it 

 can acquire a temperature of 17*5 C. The refractometer is 

 then taken from the stand, the prism thoroughly dried with a 

 soft cloth, then dipped for a moment in the first serum glass 

 and afterwards again dried. Then the prism is completely 

 immersed in the serum, and the degree of refraction read, the 

 instrument being held in one hand and the vernier manipulated 

 with the other. When the reading has been noted, the refracto- 

 meter is returned to the stand. The temperature of the bath 

 must be controlled from time to time, for the thermometer must be 

 kept at exactly 17*5C. The larger the bath, the easier it is, 

 of course, to keep the temperature constant, and the firm of Zeiss, 

 in Jena, have constructed a bath to hold forty samples for the 

 above-mentioned investigations. From time to time the refracto- 

 meter should be tested to see if at 17 '5 C. the refractive index 

 of distilled water is exactly at fifteen divisions of the scale. 



Naturally, the Zeiss-Wollny milk refractometer already 

 described can be used for these determinations. 



It is clear that the refractometer tests are particularly to be 

 recommended where the addition of water to milk has been 

 proved and the exact amount has to be determined. 



II. THE REMOVAL OF CREAM. 



A determination of the specific gravity of a sample of milk 

 often serves to indicate the addition of water, but no such 

 indication is afforded by the specific gravity when part of the 

 cream has been removed. 



The only safe method which is available is to estimate the 

 percentage amount of fat in the total solids after the quantity 

 of the latter has been calculated, with the help of Fleischmann's 

 formula, from the specific gravity and the fat-contents. The 

 fact that the specific gravity is shown to be normal, whilst the 

 amount of fat is low, must arouse attention, for under natural 

 conditions a low specific gravity implies a small percentage of 

 fat, and vice versa. 



When part of the cream is removed, or the milk diluted with 

 separated milk, there is in each case a change in the percentage 



