AGRICULTUEAL CHEMISTRY AGEOTECHNY. 207 



from zinc, and to operate with uniform amounts of reagents and milk and at the 

 same temperature. The tests here reported were conducted at from 38 to 39° C, 

 and the reagent was used in the form of tablets. The strength of the methylene 

 blue reagent may be determined by titrating it with ammonium sulphid in an 

 acid solution. 



In the investigation reported 219 samples of Swedish and Danish milks were 

 examined with the reductase and fermentation tests. Bacterial counts were 

 made parallel with the tests. For the counts a medium consisting of the fol- 

 lowing was used: Water, 1,000 gm. ; gelatin (gold), 120 gm. ; peptone (Witte), 

 20 gm. ; lactose, 10 gm. ; dextrin, 10 gm. ; sodium chlorid, 2 gm. ; dicalcium phos- 

 phate, 2 gm. ; and magnesium sulphate, 1 gm. The gelatin was neutralized 

 with phosphoric acid imtil only a slight blue color was noted with litmus paper. 

 Agar plates were less valuable for determining the bacterial content. 



The results obtained make it apparent that a very poor milk is one which 

 does not retain the blue color longer than 20 minutes and contains, as a rule, 

 over 20 millions of bacteria per cubic centimeter. Such milk is to be placed 

 into the fourth class. Poor milk, which retains the blue color longer than 20 

 minutes but not more than 2 hours, usually has a bacterial content varying 

 between 4 and 20 millions per cubic centimeter, and is put into the third class. 

 A milk of medium quality (second class) is one which will not discharge the 

 blue color within 2 hours but does in less than 5^ hours and contains, as a rule, 

 from i to 4 millions of organisms per cubic centimeter. A good milk (first 

 class) will not discharge the color within 5^ hours and contains about i 

 million of bacteria per cubic centimeter. The above criteria also holds good for 

 cream. 



It was found that there were certain exceptions to the above rule in 23 per 

 cent of the cases with milk and in 18 per cent with cream. Despite these facts 

 the reductase test is considered a good one. The fermentation test can be used 

 in conjunction with it for milks which come in the second and third classes. 



The organoleptic, leucocyte (Trommsdorff), dirt test, and direct bacterial 

 count with the microscope are also discussed. 



Hygienic investigation of market milk, G. L. J. Gk)OBEN (Centbl. Bakt. 

 [etc.^, 2. Aht., 35 (1912), No. 25, pp. 625-6Ji6) .—The production of first-class 

 milk as carried on in Holland is considered a distinct advance in milk produc- 

 tion, whereas the production of so-called " reform milks " is regarded as hardly 

 an indication of progress, since it does not come directly from the producer. 



Special or pattern milk (muster milch), should not contain more than 25,000 

 micro-organisms per cubic centimeter. The determination of the freezing point 

 is a good aid for noting milks having a normal composition, because a normal 

 milk, as a rule, has a freezing point not higher than —0.54. The test, however, 

 can not be entirely relied upon, because as Koning has shown, some normal 

 milks possess freezing points as low as — 0.515. The removal of cream usually 

 lowers the freezing point, but only when as much as one-half is removed. 



Homogenizing and sterilizing lower the freezing point of milk, and do so 

 considerably where both are combined. Heating the milk at temperatures lower 

 than the pasteurizing temperature also lowers the freezing point. 



Leather investigations: The composition of some sole leathers, F. P. Veitch 

 and J. S. RoGEES (U. 8. Dept. Agr., Bur. Chem. Bui. 165, pp. 20).— This bulletm 

 shows that the weighting of leather with useless or harmful materials is exten- 

 sively practiced in this country. The leathers examined were in part sent by 

 representative tanning companies, shoemakers, and sole cutters, and some were 

 purchased in the open market from dealers. 

 1506°— No. 3—13 2 



