FOODS 77 



solids = 12 per cent to 13 per cent. If a milk sample 

 gives a lower figure for fat or solids-not-fat than these 

 standards, adulteration is assumed to have been practised, 

 and the burden of proof to the contrary rests with the 

 vendor of the milk sampled. 



1. If the solids-not-fat figure is less than 8-5 per cent, 

 and the fat figure is 3 per cent or above, the milk has been 

 watered, and the amount of water added is calculated from 



the formula : (8-5 SnF) x ^- = percentage of added 



water. 



2. If the fat figure is less than 3 per cent, and the SnF 

 figure is 8-5 per cent or above, then fat has been abstracted, 

 usually by skimming, or already skimmed milk has been 

 added. The percentage of fat present deducted from 3 

 per cent, when multiplied by 100 and divided by 3, gives 

 the percentage of fat abstracted. (3 F) x -ip = per- 

 centage fat abstracted. 



3. If both the figures (SnF and F) are below the standard, 

 the percentage of added water should first be calculated, and 

 a further calculation made to see if the addition of this 

 amount of water would account for the lowness of the fat 

 figure. If it does not, the amount of fat removed is 

 calculated thus : The percentage of fat present deducted 

 from that found by calculation after allowing for the water 

 added is multiplied by 100 and divided by 3. Thus a milk 

 having 7-65 per cent of SnF and 2-7 per cent of F would be 

 returned as having 10 per cent of added water. If the SnF 

 are still 7-65 per cent, and the F is now 2-4 per cent, it 

 would be said to have 10 per cent of added water and 10 

 per cent of fat abstracted. 



Lactose in Milk. May be determined by the Saccharo- 

 meter (certain proteins having been first removed), or by 

 Fehling's test as now described. Take 10 c.c. of the milk 

 sample in a test tube, add a few drops of acetic acid, and 

 warm. The casein coagulates, carrying the fat with it. 

 Pour into a Nessler glass, washing out all the curd, and 

 make up the bulk to 100 c.c. Break up the curd and filter 

 several times, until whey is as clear as possible. Fill a 

 burette with the whey. Take 10 c.c. of standard Fehling's 

 solution in a porcelain basin, add 50 to 80 c.c. of aq. dest., 



