In England Hehner and Richmond have 

 worked out a formula for calculating solids as 

 follows : 



Per cent, total solids = 0.25 S. + 1.2 F. -f 0.14. 



S. is the lactometer reading and F. the per- 

 centage of fat. 



Richmond has also designed a sliding rule 

 for the rapid calculation of results (Fig. 65). 



Shaw and Eckles, who have investigated 

 the accuracy of results obtained by the use of 

 formulas, have concluded that when exact per- 

 centages of total solids are demanded the use 

 of any formula will not fulfil the requirements. 

 The authors found that the Babcock formula 

 gave results close to those obtained gravi- 

 metrically, and these results can be used when 

 only close approximations are desired. They 

 further stated that the ordinary lactometers 

 are not sufficiently sensitive for estimation of 

 total solids, but that the lactometer devised 

 by them (see p. 143) gave results as accurate 

 as those obtained with a Westphal balance. 



Fleischmann's formula for calculating total 

 solids is as follows: 



2 = 



Per cent, total solids = 1.2 F. + 2.665 



100 S. - 100 



in which F. stands for percentage of fat and S. 

 for specific gravity. 



THE DETERMINATION OF ASH 



The platinum dish containing the total 

 solids is ignited over a Bunsen flame at dull 

 red heat until a white residue is obtained. 

 This is cooled and weighed and the percent- 

 age of ash calculated. 



The following method is given by the As- 

 sociation of Official Agricultural Chemists: 



"Weigh about 20 grams of milk in a weighed 

 dish, add 6 c.c. of nitric acid, evaporate to dry- 

 ness, and ignite at a temperature just below 

 redness until the ash is free from carbon." 



When the ash is to be further analyzed for 

 its elements the following method can be em- 

 ployed (Richmond): 



179 



