MANUFACTURE OF CASEIN. 31 



When the sets of test papers having an increase of one gram in 

 casein for each succeeding set are perfectly dry, a short stick of seal- 

 ing wax softened by heating at one end is applied with a fairly firm 

 pressure to various points where the coating is uniform, and allowed 

 to cool. The paper is then held down firmly by placing the fingers 

 on each side of the wax and the latter pulled away with a steady pull. 

 In case of an insufficient quantity, of casein the wax will pull only 

 the clay mixture, but when sufficient casein has been used it will 

 pull the paper fibers strongly to the edge of the wax, showing that 

 the coating material had actually become a part of the paper. 

 Usually a transition point is found when the center of the stick of 

 wax will pull the paper fibers partially, while the next set having 

 1 gram more of casein will pull all the fibers to the extreme edge 

 of the wax. A good grade of casein should not require more than 

 8 or 9 grams to hold strongly. 



The strength of the casein as shown by this laboratory test bears 

 some direct relation to the quantity of casein necessary to use in the 

 practical coating work, and for that reason was used in determining 

 the influence of the various factors observed upon the strength of the 

 casein. 



SOLUBILITY TESTS. 



Weigh out 50 grams of air-dried sample ground to pass through a 

 20-mesh screen, add 300 cubic centimeters of distilled water in which 

 7.5 grams of commercial borax has been dissolved. Heat in a beaker 

 or other flask in a water bath having a temperature not to exceed 

 149° F. (65° C.). Complete solution should result within 10 minutes. 

 149^ F. (65° C). Complete solution should result within 10 minutes 

 with continuous stirring. 



CASEIN MARKETS AND PRICES. 



The market for skim-milk casein, which is the only kind that has 

 been made in large quantities in the past, has always been good at 

 the prevailing prices. A few years ago the price received for it was 

 from 5 to 7 cents a pound, but during the last two years, owing to the 

 falling off in the importation, the price has doubled or trebled. At 

 one time the exceptionally high price of 22 cents a pound was offered, 

 with very little available. This price was exceptional, of course, and 

 did not prevail for a great length of time. The demand during the 

 last two years has been steady despite the exceedingly high prices. 

 While the market will readjust itself with a resumption of normal 

 conditions the price, in all probability, will not go back to what it 

 was a few years ago. The large users are frank in admitting that 

 they will not be able again to purchase the product at the former 

 low prices. 



