326 



PHYSIOLOGICAL CHEMISTRY 



The accuracy of the method compared with that of the Soxhlet method, 

 using the paper-coil modification and extracting until fresh portions of absolute 

 ether gave no further trace of extractive material, is shown by the average 



difference on twelve samples of human milk 

 being only 0.017 per cent less than by the 

 Soxhlet and on seven samples cow's milk being 

 only 0.019 per cent less. The extreme differ- 

 ences in case of the human milk were 0.004 

 per cent and 0.044 per cent and in case of 

 the cow's milk 0.006 per cent and 0.068 per 

 cent. 



(c) Adams' Paper-coil Method. Introduce 

 about 5 c.c. of milk into a small beaker, quickly 

 ascertain the weight to centigrams, stand a fat- 

 free coil 1 in the beaker and incline the vessel 

 and rotate the coil in order to hasten the absorp- 

 tion of the milk. Immediately upon the com- 

 plete absorption of the milk remove the coil and 

 again quickly ascertain the weight of the beaker. 

 The difference in the weights of the beaker at 

 the two weighings represents the quantity of 

 milk absorbed by the coil. Dry the coil care- 

 fully at a temperature below iooC. and extract 

 it with ether for 3-5 hours in a Soxhlet appa- 

 ratus (Fig. 108). Using a 

 safety water-bath, heat the 

 flask containing the fat to 

 constant weight at a tempera- 

 ture below iooC. 



Calculation. Divide the 

 weight of fat, in grams, by 

 the weight of milk, in grams. 

 The quotient is the percentage 



FIG. 108. SOXHLET APPARATUS, of fat contained in the milk 



examined. 



(d) Nephelometric Method of Bloor. 2 This method is ex- 

 actly similar in principle and procedure to the method given 

 for the determination of fat in blood. (See page 295.) One 

 c.c. of milk is ordinarily taken. 



(e) Approximate Determination by Feser's Lactoscope. Milk 

 is opaque mainly because of the suspended fat globules and 



therefore by means of the estimation of this opacity we may obtain data as to 

 the approximate content of fat. Feser's lactoscope (Fig. 109) may be used for 

 this purpose. Proceed as follows: By means of the graduated pipette accompany- 

 ing the instrument introduce 4 c.c. of milk into the lactoscope. Add water gradually, 

 shaking after each addition, and note the point at which the black lines upon the 

 inner white glass cylinder are distinctly visible. Observe the point on the graduated 



1 Very satisfactory coils are manufactured by Schleicher and Schiill. 



2 Bloor: /. Am. Chem. Soc., 36, 1300, 1914. 



