1532 



INDUSTRIES DEPENDING ON ANIMAL PRODUCTS 



INDUSTRIES 



DEPENDING ON 



ANIMAL 



PRODTTCTS 



value decreased. Exceptions to this rule were the oil of " I vSano " and the 

 fat of Ricinodcndron africanus. 



4) No relationship could be traced between the index of refraction and 

 the remaining constants, i. e. acidity value, Reichert and Hehner numbers. 



5) With regard to the influence of the chemical composition on the in- 

 dex of refraction, it is obvious that the value of the latter must be dependant 

 on the actual constitution of the fat or oil. Inasmuch as each fat or oil 

 consists of mixture of the fatty acids or of the glycerides of the fatty acids, 

 the refractive index of the whole substance must be influenced by the re- 

 fractive indices of its component parts. 



If the fat or oil be a true mixture and the optical characters of each of 

 its constituents were known it should be possible to calculate either its 

 refractive index from a quantitative chemical analysis or vice versa. But 

 up to the present no other refractive indices beyond those of stearic, palmi- 

 tic and oleic acids have been determined and the indices of all the glycer- 

 ides have still to be investigated. Under these conditions it is very diffi- 

 cult to say with am' degree of certainty whether fats and oils really consist 

 of true mixtures and whether it will ever be possible to check experimental 

 results by calculated values. The only example at present available in 

 this connection is the fat of Pentadesma hidyracea v/hich consists of 90 per 

 cent of stearic and palmitic acids with 10 per cent of oleic acid. Its re- 

 fractive index works out to 0.512 at 79° C. ; practical tests gave 0.530. 



1119-The Grading of Milk. — Kelly, E. in Hoard's Dairyman, Vrl. Lll, No. i, pp. i 

 and (:. I-'ort Atkinson, Wis., July 28, 191 6. 



The grading of milk is made necessary by the fact that it costs more 

 to produce milk of one quahty than of another, and that the producer 

 ought to be paid accordingly. A first attempt to sell a ver\- pure milk 

 in the United States was made about 25 years ago when a " certified " milk 

 was put on the market in New Jersey. This was intended for infants and 

 invalids and was produced under strict medical superAdsion and at a great 

 expense. vSince then several health departments have granted permits 

 for the sale of " inspected " mJlk which is not of such high quahty as the 

 certified milk, but still considerably better than the average supply. vSuch 

 inspected milk usually fetches one or two cents per quart over and above 

 the current price. 



Grading may be done either by the milk dealer from purely business 

 motives, or by the town or state officials for the benefit of the consumers. 

 Three principal factors determine the quality of the milk, i. e. its fat content^ 

 the number of bacteria it contains, and the sanitary condition of the dairy 

 farm where it has been produced. »Some dealers grade milk on the fat 

 content alone, others only on the standard of the cleanliness at the dairy 

 farm, while a few health authorities simply use the bacterial counts. 



As an example of payment for graded milk : one large dairy compan3^ 

 buys on a schedule in which prices are quoted for each month and for milk 

 with a fat content ranging from 3 to 4.2 per cent. During the six winter 

 months a difference of 4 cents per point is made for each 100 lbs. of milk; 

 in summer the dift'erence is 3 cents per point. This amounts to 40 cents 



