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COMPOSITION AND PROPERTIES OF MILK 299 



the divisions representing the percentages 

 of fat and non-fatty solids. For practical 

 purposes, the lines are more conveniently 

 drawn on a piece of wood, of which the 

 middle portion, corresponding to the line 

 x'x, is movable. Such an arrangement is 

 shown in Fig. 25. It is called a milk scale. 



Richmond's Scale. This apparatus is 

 very similar in form to that shown above, 

 and the two diagrams may be regarded as 

 the theoretical basis of its construction. 

 The chief difference between Richmond's 

 scale and that shown in Fig. 25 is that the 

 former is graduated to show the percentages 

 of total solids, i.e. non-fatty solid plus fat, 

 instead of percentages of non-fatty solids ; 

 and it is provided with a secondary scale, 

 by means of which the specific gravity may 

 be corrected for temperature in a similar 

 mechanical manner. Also, in Richmond's 

 scale, the percentages of fat are marked on 

 the upper line, and those of the total solids 

 on the lower; and the numbers are in 

 reverse order, so that the scale reads from 

 right to left. 



Formulae. The fact, stated above, that 

 the specific gravity of milk is increased 4 of 

 the lactometer by each i per cent, of non- 

 fatty solids, and is lowered o'8 by each i 

 per cent, of fat, may be expressed as a 

 formula, thus 



G = 4N - o-8F 



G is the number of lactometer degrees, 

 and F and N are respectively the percen- 

 tages of fat and non-fatty solids in the 

 milk. 



The specific gravity and percentage of 



goo 



"o - 



<o - 



u. 



(M 



