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 cla}^ mixture, but when sufficient casein has been used it will 
pull the paper fibers strongly to the edge of the Avax, 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 
14:9° F. (65° C). Complete solution should result within 10 minutes. 
149J 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. 
