438 EXPERIMENT STATION RECORD. 



pepsin dissolved in about 1 cc. of water. The whole was then stirred with a platinum 

 wire and left for about 2 hours at 40° C, and then at room temperature until the 

 following day, when as much of a mixture of 9 volumes of granular kaolin and 1 

 volume barium carbonate was added as was necessary to absorb completely the con- 

 tents of the dish. The material was then placed in a drying oven for 4 to 5 hours 

 at about 98° C, and the desiccated mass finally extracted with anhydrous ether. 

 The pepsin used was found free from ether-soluble substance-. 



The author concludes that the Gottlieb method gives correct results, and should 

 be used to the exclusion of the extraction methods in the analysis of milk low in 

 fat. — f. w. WOLL. 



Contribution to the detection of watered milk, (). Bialon (Milchw. ZentbL, 

 1 (1905), No. 8, i>[>. 363-366).— The specific gravity of milk serum is shown to vary 

 irregularly with the method of coagulation employed. 



In one instance the specific gravity of the serum obtained by spontaneous coagu- 

 lation was 1.0284, by acetic acid- 1.0266, and by rennet 1.0291. The variations are 

 explained as due to the different amounts of phosphates, lime, and proteids left in 

 solution. Complete analyses showed furthermore that the properties of the serum 

 obtained by the same method are not constant. Instead of using determinations of 

 total solids and specific gravity of the serum, the author would make use of the spe- 

 cific gravity of the fat-free milk determined by the formula: 



100s -f 



6= 



10 °-oi33 



in which s represents the specific gravity of the milk, f the percentage of fat, and 

 0.933 the average specific gravity of milk fat. For pure milk 6 or the specific gravity 

 of the fat-free milk was found to be about 1.0323. 



On the basis of a large number of determinations, the author concludes that a spe- 

 cific gravity of 1.0323 or above calculated by this formula shows that the milk is 

 unadulterated, while a lower figure shows that water has been added. The method 

 is, of course, not applicable to curdled milk. 



Refractometric examination of milk, M. Hexseval and G. Millie (Rev. Gen. 

 Lait, 4 (1905), No. 23, j>p. 529-538). — Ripper's method of preparing the serum is 

 preferred. This consists in adding 1 cc. of 20 per cent acetic acid to 50 cc. of milk, 

 heating on a water bath to 65 to 70° C. for 5 minutes, cooling to 15° and filtering. 

 The determination of the index of refraction may be made at room temperature and 

 calculated to 15° by adding or subtracting 0.000117 for each degree that the room 

 temperature is respectively above or below 15°. 



The index of refraction of normal serum varies from 1.3429 to 1.3445. The prin- 

 cipal refractive substances in the serum are lactose, salts, and albumin. The addition 

 of 10 per cent of water to milk causes a decrease of about 0.00102 in the index of 

 refraction. A lower index than 1.3425 maybe accepted as an indication of watering. 

 An abnormally high index would warrant a suspicion that soluble substances had 

 been added. 



The authors did not find that the index of refraction of the milk of diseased cows 

 was always low, not even when a positive tuberculin reaction was obtained. Such, 

 however, was often the case in mammary tuberculosis, but in those instances the 

 milk could generally be recognized by its abnormal appearance. The milk of the 

 healthy quarters showed a normal index. The lowering of the index was found due 

 to a diminution of the lactose. 



Cryoscopy of milk for detecting- the addition of water, C. Bartitel (Rev. 

 Gin. Lait, 4 (1905), No. 22, pp. 505-512) . — Numerous determinations are reported 

 which go t<> show that the freezing point of milk is not appreciably affected by the 

 individuality or breed of cows, the quarter of the udder from which the milk is 

 obtained, the fat content of the milk, estrum, etc., but that it is very constant between 



