DAIRY PRODUCTS. 128 



2. Total Solids. 



Dilute a measured portion of the above 40 per cent solution with an equal 

 amount of water, use 5 cc of the diluted mixture, corresponding to 1 gram of 

 the condensed milk, and proceed as directed under ' Milk," page 117. 



3. Ash. 



Ignite the total solids at very low redness, cool, and weigh. 



4. Proteids. 



Determine nitrogen according to the Kjeldahl or Gunning method ("I. Fer- 

 tilizers," p. 5) in 5 cc of the 40 per cent solution and multiply by 6.38. 



5. Lactose. 



Dilute 5 cc of the 40 per cent solution to about 40 cc and add O.G cc of 

 Fehling's copper solution. Nearly neutralize with sodium hydroxid, make up 

 to 100 cc, filter through a dry filter, and determine lactose in an aliquot as 

 directed under " VI. General Methods," page 48. 



6. Sucrose. 



Determine by difference, deducting the milk solids (lactose+proteids+fat+ 

 ash) from the total solids. 



7. Fat or Ether Extract. 

 (See also Appendix, p. 253.) 



Place 15 cc of the 40 per cent solution in a Babcock test bottle. Fill the 

 bottle nearly to the neck with water, add 4 cc of Fehling's copper solution, shake 

 thoroughly and rapidly, separating the precipitated proteids and fat by means 

 of a centrifuge," or the precipitate may be allowed to settle, which it does 

 more quickly in the cold. Withdraw the supernatant 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 by 

 shaking with water, separating the precipitate, 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 

 hi the sample. 



BUTTER AND ITS SUBSTITUTES. 



1. Preparation of Sample. Official. 



If large quantities of butter are to be sampled, use a butter trier or sampler. 

 Completely melt the portions thus drawn, 100 to 500 grams, in a closed vessel 

 at as low a temperature as possible. When melted, cool the whole, and at the 

 same time shake the mass violently until it is homogeneous and sufficiently solid- 

 ified to prevent the separation of the water and fat. Then pour a portion into 

 the vessel from which it is to be weighed for analysis. The sample should 

 completely or nearly fill the vessel and should be kept in a cold place until 

 analyzed. 



While the steam-driven centrifuge may be used, 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 

 Vf&sa. 



87404 Bull. 107- 



