THE ANALYSIS OF MILK II 



and the empty tube gives its capacity in grammes of 

 water at 15.5. 



Empty the water, and rinse the tube several times 

 with the milk, and then fill it with milk ; allow the 

 tube to stand a minute to permit air bubbles to rise, 

 suck or blow these out, and fill the tube completely. 

 Immerse the tube in water at 15.5 C. till the 

 volume ceases to alter, and then wipe dry and weigh as 

 before. The difference between the full and the empty 

 tube gives the weight of milk, and this divided by the 

 capacity in grammes of water at 15.5 gives the specific 

 gravity at 15.5. 



The capacity of the tube once determined remains 

 constant, and it need not therefore be determined every 

 time ; the weight of the empty tube should, however, 

 be taken occasionally. 



Rise of Specific Gravity of Milk on Standing. 

 If the milk is freshly drawn or has been recently 

 heated, the fat is in the liquid condition, and its specific 

 gravity is lower than when solid. The solidification 

 of the fat globules takes some time, and twelve to 

 twenty-four hours may elapse before the maximum 

 specific gravity is attained. If the milk is frothy, 

 air bubbles may cause the specific gravity to appear 

 too low. 



The maximum specific gravity is taken as the correct 

 figure. 



Estimation of Total Solids. Weigh a basin either 

 of platinum, tantalum, fused silica, or porcelain, prefer- 

 ably 2f in. wide and flat-bottomed; pipette in 5 c.c. of 

 milk and weigh again ; the weighing should be rapid, 

 but the exactitude of weighing need not be more than 

 2 mg. Place the basin on a water-bath (Fig. 8), and 

 from time to time break the skin with a needle ; when 

 apparently dry place in a water-oven (Fig. 9), and 

 continue the drying for four hours, cool in a desiccator, 

 and weigh ; replace in the oven for periods of one hour 

 each, cool and weigh, until the loss in one hour is less 

 than i rag. The weight of the residue divided by the 



