Estimation of Solids not Fat 107 
found to represent about the amount occupied by 
the curved surfaces in the neck of the bottle, 
due to the capillary attraction between the fat and 
the glass. 
Cleaning the glassware.—Good results cannot be 
secured unless the glassware is kept clean and 
bright. This can easily be done with very little 
trouble. As soon as the bottles are read, and while 
they are still hot, the contents should be emptied 
out. The hot acid and water will carry out with 
it the larger part of the fat in the neck of the 
bottle. The emptied bottle should then be rinsed 
once in warm water and once in hot water containing 
some alkali, either washing soda: or any of the va- 
rious washing powders, and then rinsed with either 
warm or cold water until they are perfectly clean. 
With these precautions no difficulty will be expe- 
rienced in keeping the bottles clean and bright. 
By the use of the lactometer in connection with 
the percentage of fat, a close approximation to the 
percentage of total solids, or, solids not fat, may be 
made. Numerous formule for this purpose have 
been devised. Their application is explained and il- 
_ lustrated in Part A of the Appendix. 
