XXII] DAIRY PRODUCTS 293 



28 GELATIN.-TENTATIVE. 

 Proceed as directed under 19. 



29 COLORING MATTERS.— TENTATIVE. 



Proceed as directed under XI, particularly 3 and 24 for the detection of oil- 

 soluble coal tar dyes and annatto. 



30 PRESERVATIVES.-TENTATIVE. 

 Proceed as directed under X. 



31 CONDENSED MILK (UNSWEETENED). 



Dilute 40 grams of the homogeneous sample with 60 grams of water and pro- 

 ceed as directed under 1 to 15, inclusive, 19, 20 and 21, correcting the results for 

 the dilution. 



CONDENSED MILK (SWEETENED). 



32 PREPARATION OF SAMPLE.-OFFICIAL. 



If cold, place the can in water at 30°-35°C. until warm. Open, scrape out all 

 milk adhering to the interior of the can and mix by transferring the contents to a 

 dish sufficiently large to stir thoroughly and make the whole mass homogeneous. 

 Weigh 100 grams into a 500 cc. flask and make up to the mark with water. If the 

 milk will not dissolve completelj', weigh out each portion for analysis separately. 



33 TOTAL SOLIDS.-OFFICIAL. 



Use 10 cc. of the solution, prepared as directed in 32, and proceed as directed in 

 1 , drying either on sand or asbestos fiber. 



34 ASH.— OFFICIAL. 



Evaporate 10 cc. of the solution, prepared as directed in 32, to dryness on a 

 water bath and ignite the residue as directed under VIII, 4. 



35 PROTEIN.— OFFICIAL. 



Determine nitrogen as directed under I, 18, 21 or 23, using 10 cc. of the solu- 

 tion, prepared as directed in 32, without evaporation and multiply by 6.38. 



38 LACTOSE.-OFFICIAL. 



Dilute 100 cc. of the solution, prepared as directed in 32, in a 250 cc. flask to 

 about 200 cc, add 6 cc. of Fehling's copper sulphate solution [VIII, 19 (a)] and make 

 up to the mark. Filter through a dry filter and determine lactose as directed in 



VIII, 46 or 48. 



37 FAT OR ETHER EXTRACT. 



Roese-Gottlieb Method.— Official. 



Weigh 4-5 grams of the homogeneous sample into a Rohrig tube or some similar 

 apparatus, dilute with water to about 10.5 cc. and proceed as directed under 12. 



38 SUCROSE.-TENTATIVE. 



Determine sucrose by difference, deducting the milk solids (lactose, protein, fat 

 and ash) from the total solids. 



