18 Director’s REPORT OF THE 
which in Bulletin 215 was called casein monolactate, but which 
by more recent work we have found to be free casein; in the 
second stage, after the formation of more acid, the casein unites 
with this acid to form a compound which is the familiar solid 
substance of sour milk and which constitutes a large part of the 
dry matter of cottage cheese. The conditions of temperature 
were ascertained for the best yield and quality of cottage cheese. 
Success was attained in making good cottage cheese from milk 
by direct addition of hydrochloric acid, thus shortening the time 
- of manufacture from one or two days to as many hours. It was 
found that very slight chemical change occurs in cottage cheese 
after it is made, and in this respect the behavior of cottage cheese 
is wholly unlike that of cheddar cheese. According to popular 
belief, cottage cheese is more readily digested than cheddar cheese, 
and this belief was supported by artificial digestions of the two 
kinds. 
The composition of commercial whale-oil soaps in relation to 
spraying.—Many complaints have been received from fruit-grow- 
ers in regard to the unsatisfactory results given by con:mercial 
whale-oil soaps in spraying fruit trees. In some cases the insects 
were not killed, while in other cases the foliage was seriously 
injured. In response to inquiries on this subject, an investiga- 
tion was undertaken to study the composition of the commercial 
whale-oil soaps commonly found in the market. It was found 
that these soaps vary greatly in composition. Different lots of 
soap from the same factory were found to contain actual soap 
varying from 24 to 46 per ct. So great is the variation in com- 
position of these soaps that they cannot be relied upon at all 
for giving uniform results. Since manufacturers are unwilling 
to furnish commercial whale-oil soap of guaranteed composition, 
experiments were made resulting in the recommendation of a cer- 
tain formula for home-manufacture of fish-oil soap. The home- 
made soap destroys plant lice and does not injure foliage; it costs 
less and can be relied upon to give uniform results. In addition, 
a study was made of the amount of free-alkali in soap that will 
do injury to foliage. Soaps containing less than five per cent. of 
free alkali did no injury under the conditions employed. Full de- 
tails are given for the home-making of fish-oil soap, and addresses 
are given of parties who will furnish materials. : 
