86 SCIENCE AND PRACTICE OF DAIRYING. 



hydrogen, air is drawn through and it is weighed. If, after weighing, 

 the metallic copper is dissolved in dilute nitric acid, the tube, after being 

 washed out and dried, but reduced 10 to 15 nig. in weight, may be used 

 again. The estimation of the milk-sugar from the weight of the copper, 

 after Soxhlet : 



392-7 mg. copper represent 300 mg. milk-sugar. 



363-6 275 



333-0 250 



300-8 225 



269-6 200 



237-5 175 



204-0 150 



171-4 125 



138-3 100 



For example, if the copper found weighs -291 grams, according to the 

 table this shows 



225 x. 291 _ 

 300-8 



grams of milk-sugar in 5 c.c., that is, 4'354 grams in 100 c.c. of milk, or, 

 if 100 c.c. of milk weigh 103'1 grams, 4*223 per cent of milk-sugar. 



The filtrate which is obtained in the Ritthausen process as above 

 described in the determination of the proteid substances may be used for 

 the determination of the milk-sugar. 



Determination of the Ash. 25 grams of milk, after the addition of a few 

 drops of acetic acid, are heated to hard dryness on the water-bath in a 

 platinum capsule, and then slowly incinerated over an open flame. The 

 residue, after being boiled several times with water, is burned to a white 

 ash. The platinum capsule is then placed in a water -bath, the watery 

 extract slowly added, evaporated, and then slowly ignited, allowed to 

 cool, and weighed. If milk samples which have been already weighed out 

 for investigation are not immediately analysed, care must be taken that 

 they are kept at a temperature under 12 C., and for only about 48 hours. 

 If the samples are kept longer or are placed in a higher temperature, 

 considerable loss in the total solids may be expected. 



In addition to what has been above described, we may add one or two 

 details with regard to points which may crop up in the testing of milk. 

 In the year 1883, Uffelmann suggested that since ordinary spring and river 

 water almost always contained ammonia, nitric acid, or nitrates, bodies 

 which are never found in uncontaminated milk, these might be taken as 

 an indication of the addition of small quantities of river water to milk. 

 Unfortunately, however, the proof of the addition of water to milk 

 through the diphenylamine reaction of nitrates and nitric acid is not of 



