504 EXPEEIMENT STATION EECORD. 



of citric acid to 250 cc. of solution), fill up to the 100 cc. mark, and after stand- 

 ing for 15 minutes filter and polarize. One degree of rotation to the right in 

 circular instruments and sodium light at 20° C. in a 200 mm. tube==0.9518 gm. 

 of milli sugar. If the rotation X0.9518=a, the lactose content M= 



96.7-/) a 



100.8-i+ 



75 

 a- 



75 

 i=percentage of total solids and /=percentage of fat in milk. 



The estimation of the viscosity of milk as an aid for detecting added 

 water, W. D. Kooper (MilcMv. ZentU., Jf3 (1914), Nos. 7, pp. 169-179, fig. 1; 8, 

 pp. 201-208). — In these studies composite milks were principally examined. 

 The apparatus used is illustrated and described. 



The expression of the viscosity is analogous to that used by Engler in report- 

 ing the viscosity of oils. The degree of viscosity in the milk seems to be an 

 expression of the total solids content and its determination will enable one to 

 detect added water or the removal of cream. With the method at least 5 per 

 cent of water may be found. The fat content of the milk apparently does not 

 influence the viscosity to the extent suggested by Micault,*^ and although an in- 

 creased fat content is expressive of an increased viscosity there are instances 

 where the reverse is the case. A still smaller relation exists between the specific 

 gravity and the viscosity. A milk diluted with 25 per cent of added water has 

 a higlier viscosity than unadulterated milk. If, however, the viscosity obtained 

 is divided by the factor 0.1384 the total solids content of the milk may be ap- 

 proximately estimated. 



Detection of goat's milk in cow's malk, J. Pkitzkeb (Chem. Ztg., 38 (1914), 

 No. 93, pp. 982, 983; ahs. in Jour. 8oc. Chem. Indus., 34 (1915), No. 4, p. 195).— 

 The test depends upon the difference in behavior of the two milks with ammonia. 



The freezing point of some abnormal milks, J. B. Henderson and L. A. 

 Meston (Proc. Roy. Soc. Queensland, 26 (1914), pp. 85-90; ahs. in Jour. Soc. 

 Chem. Indus., 34 (1915), No. 4, P- 195). — Two samples of mixed milks from eight 

 animals, badly fed and in poor condition, were found to be low in solids not 

 fat (7.74 and 7.79 per cent) but had a normal freezing point ( — 0.55 and 

 — 0.54° C). When the milk from each animal was examined only one of them 

 was found to give a normal milk, but in every case the freezing points were 

 within the normal limits ( — 0.54 and — 0.56°). The ash of the milk contained 

 large amounts of chlorin (up to 31 per cent) . This is regarded as evidence of the 

 power of the mammary glands to regulate the osmotic pressure through the 

 extraction of an increased amount of sodium chlorid from the blood in order 

 to compensate for the deficiency of other constituents. 



The electrical conductivity of milk during its concentration, with sugges- 

 tions for a practical method of determining the end point in the manufac- 

 ture of sweetened condensed milk, Lilias C. Jackson, L. McNab, and A. O. H. 

 KoTHERA (Jour. Soc. Chem. Indus., 33 (1914), ^o. 2, pp. 56, 60). — The maxi- 

 mum electrical conductivity is noted when morning milk is concentrated to 28 

 per cent total solids with 8 per cent protein. Evening milk gives higher figures. 

 The electrical conductivity is deemed of no value in determining the degree of 

 concentration of a separated unsweetened milk because the concentration may 

 increase considerably between 25 and 30 per cent of total solids with very little 

 alteration in the conductivity. " It is quite different, however, with a sweetened 

 milk concentrated to the degree which is usual in the manufacture of condensed 

 milk. With full fat, and with added cane sugar equivalent approximately to 

 16 lbs. sugar per 100 lbs. milk, the reversal of the conductivity comes at the 



"Ann, Cliim. Analyt, 9 (1904), No. 9, pp. 93-96. 



