formed, preferably adding a few drops of strong ammonia to aid in the softening and 

 emulsionizing, and keep the beaker in hot water till the emulsion is tolerably com- 

 plete and free from lumps. 



If the sample is a full-cream cheese a Babcock cream bottle is employed. The 

 contents of the beaker, after cooling, are transferred to the test bottle as follows: Add 

 to the beaker about half of the 17.6 cc of sulphuric acid regularly used for the test, 

 stir with a rod and pour carefully into the bottle, using the remainder of the acid in 

 two portions for washing out the beaker. Finally proceed as in the Babcock test f r 

 milk. Multiply the fat reading by 18 and divide by the weight of the sample take., 

 to obtain the per cent of fat. 



On page 41, at the end of the methods for dairy products, insert the 

 following as a provisional method: 



(D) CONDENSED MILK. 



Preparation of the sample. Mix thoroughly by transferring the contents of the can 

 to a large evaporating dish and working it with a pestle until homogeneous. Weigh 

 40 grams of the mixed sample in a 100 cc flask, or transfer thereto by washing, and 

 make up to the mark with water. 



Total solids. Dilute a measured portion of the above 40 per cent solution with an 

 equal amount of water, and transfer by a pipette 5 cc of the diluted mixture, cor- 

 responding to 1 gram of the condensed milk, into a tared platinum dish, which is 

 allowed to remain in contact with the live steam of a water bath for at least two 

 hours after the last traces of water have been evaporated to leave an apparently dry 

 residue. Transfer to a desiccator, cool, and weigh. 



Ash. Carefully ignite the residue from the total solids, cool, and weigh. 



Fat. Measure 15 cc of the above 40 per cent solution, corresponding to 6 grams 

 of the condensed milk, into a Babcock test bottle. Fill nearly to the neck with 

 water and add 4 cc of Fehling's copper solution, shake thoroughly and rapidly, sep- 

 arating the precipitated proteids and fat by means of a centrifuge, & or the precipitate 

 may be allowed to settle of itself, which it does more quickly in the cold. Withdraw 

 the supernatant sugar-containing liquid by means of a small stemmed pipette with a 

 wisp of wet absorbent cotton twisted over the bottom to serve as a filter. Wipe off 

 the cotton into the bottle on withdrawing the pipette. Give the precipitated proteids 

 and fat two additional washings as above by shaking with water, separating the pre- 

 cipitate, and removing the washings with the pipette. If the precipitate is caked 

 hard after centrifuging, use a stiff platinum wire as a stirrer. Finally add water to 

 an approximate volume of 17.5 cc and 17.5 cc of sulphuric acid, and continue the 

 test as in the Babcock process of milk testing, multiplying the reading by 3 for the 

 percentage of fat in the sample. 



a Leach, J. Am. Chem. Soc., 1900, 22 : 589. 



& While the steam-driven centrifuge may be used for this, it is better to centrifuge in the cold, 

 since the heat of the steam-driven machine cakes the precipitate so that it is harder to 

 wash. 



Proteids. Dilute 5 cc of the 40 per cent solution, corresponding to 2 grams of the 

 sample, to about 40 cc and add 0.6 cc of Fehling's copper solution. Nearly neutral- 

 ize with sodium hydroxid, stopping just short of alkalinity. Pass through a weighed 

 filter paper, wash, dry at 100 C., and weigh. Burn the precipitate in a porcelain 

 crucible, the difference between the weight of the dry precipitate and the weight of 

 the ash being the weight of the proteids and fat. Expressing this in percentage and 

 deducting the per cent of fat previously obtained, the result is the per cent of 

 proteids. 



Milk sugar. Make up the filtrate and washings from the previous operation to 100 

 cc and determine the lactose either gravimetrically or volumetrically in this solution. 



