576 



to these experiments, it does not seem profitable to feed more than 

 13.2 pounds of non-protein* per head of neat cattle or ten head of 

 sheep per day. (2) There is no objection to feeding considerably more 

 protein than current usage and feeding standards call for. The advan- 

 tage rests partly in the increased production and partly in the higher 

 value of the manure. 



An account of some more recent experiments on the feeding value of 

 wet vs. dry diffusion residue of beets will be given in the next number 

 of the Record.— [W. O. A.] 



Testing milk by means of electricity, W. Thdrner {Chem Ztg., 

 15 [1891), pp. 1073, 1074). — The autlior claims to have conceived the idea 

 of arriving at the percentage of water and fat in milk by measuring 

 the resistance which milk j^resents to a current of electricity, previous 

 to the announcement of Dolirniann's experiments (see Experiment Sta- 

 tion Record, vol. iii, p. 421 ), and that the results recorded below were 

 made independently of Dohrmann. In his experiments he used an 

 instrument on which from 0.1 to 10,000 ohms could be quickly and accu- 

 rately measured. 



The experiments were all conducted in a flat-bottomed glass dish, 

 filled to the same de]>th with milk each time, and all measurements 

 were made at 17^ C, with a distance between the eh'<tro(U's of 5 cm. 

 His first experiments were made with seventeen sami)les of milk, con- 

 taining ditterent percentages of butter fat and of difterent degrees of 

 aridity. The results showed that in fresh market milk of from 9° to 

 17° of acidity there was no considerable variation in the resistance, 

 the latter being between 180 and 210 olims; and that the resistance 

 which the milk offered was entirely independent of the percentage of 

 butter fat it contained. Even after a ])art of the cream had been 

 removed the resistance remained principally the same, in case no change 

 in the acidity had occurred. It would seem, then, that butter fat, a very 

 poor conductor of electricity, when suspended in a good conducting 

 medium (milk serum) had only a slight ett'ect on the conductibility of the 

 medium. Tlie author therefore believes it to be shown that it is not 

 possible to gain an idea of the fat content of the milk by measurement 

 of its electrical resistance. 



He then made a series of tests to determine whether by this method 

 the watering of milk could be detected. Since, according to his own 

 observations, waters of diflerent composition present different resistance 

 to an electric current, six difterent kinds of water were included in the 

 test. Samples of milk received additions of ditterent amounts of each 

 of these waters. When the watered milks were tested they showed that 

 the conductivity of the milk was diminished by an addition of water in 

 proportion to the quantity added and the purity of the water, the purer 

 the water the greater being the resistance. It was further found that 



'Estimating by assuming the calorific vahie of the actual fats as equal to two and 

 a half times the same weight of carbohydrates and multiplying the weight of the 

 former by this factor and adding it to the latter. 



