Condensed Milk and Milk Powder 201 



only, when the range of temperature is within the limits of 55 

 degrees and 65 degrees F. 



The specific gravity is calculated by adding 1000 to the lactom- 

 eter reading and dividing the sum by 1000. Example: Lactometer 

 reading is 31 at 65 degrees F. Corrected reading is 31.5; 



31.5 + 1000 

 specific gravity is = 1.03 15. 



Gravimetric Determination. — This consists of the filling of 

 a perfectly dry picnometer or other graduated flask of known 

 measure, with milk at the ■standard temperature ; (6o degrees F., or 

 15.5 degrees C.) and weighing the flask and contents. The weight 

 of the flask is then deducted from the weight of the flask plus con- 

 tents and the difference is divided by the weight of an equal volume 

 of water at standard temperature. The result is the specific gravity 

 of the milk. 



The Westphal balance method furnishes another accurate 

 means of determining the specific gravity. Both,' the gravimetric 

 method and the Westphal balance method, while accurate when 

 operated by the skillful chemist, require considerable time. Ex- 

 perimental comparisons have demonstrated that, for all practical 

 purposes, the Quevenne hydrometer, when accurately graduated, 

 yields correct results, and the simplicity and rapidity of its operation 

 render its use in the determination of the specific gravity of milk 

 highly advantageous and satisfactory. 



TOTAL SOLIDS 



By Means oe the Babcock Formula. — For rapid and reason- 

 ably accurate work the total solids of milk are best determined by 

 the use of the Babcock formula, which is as follows : 



L 



Total solids = + 1.2 x f. 



4 



L = Quevenne lactometer reading. 



f = per cent, of fat. 



Example: Lactometer reading is 32; per cent, fat is 4. 



32 

 Total solid's = + 1.2x4= I2 -8 per cent. 



