86   Report of Wisconsin Dairy and Food Commissioner


butter. That is, they were found to contain 80 per cent or more of milk
fat. Eighty-two of these samples were found to be below the legal
standard in that they contained less than 80 per cent of fat. None of
the samples submitted by our inspectors were found to contain foreign
fat.
In reports the work of the laboratory for the years 1919 to 1922, in-
clusive, certain facts pertaining to the manufacture of butter were
taken up and very thoroughly discussed with the view of supplying
information to manufacturers of butter, which, it was thought, would
be useful to them. Among the problems discussed was the great varia-
tion in the salt content found from our analytical work in the labora-
tory on commercial butters, also the question of how near the butter
maker might be expected to come to a maximum moisture content of
16 per cent without laying himself liable. The influence of the quality
of cream on the finished product was taken up and therefore a con-
sideration of these subjects at this time seems unnecessary.
A limited amount of experimental work was carried on in the labora-
tory in connection with one of the creamery and cheese factory in-
spectors to determine the practicability of the use of 'the so-called
gasoline test to determine the fat content of butter at creameries. This
is not a new method and has been in use in some creameries. In 1916
in the Dairy Department of the University of Illinois, Edward F.
Kohman worked out the details of this method, using petroleum ether
and gives the results of analyses on ten samples of butter. Duplicate
determinations were made by his method and compared with the re-
sults obtained by the official methods of the Association of Official
Agricultural Chemists. The method of determining fat is as follows:
A ten gram sample of butter is weighed out in a moisture dish on a
moisture scale and the moisture determined in the usual way. When
the moisture determination is completed, the fat is determined in the
same sample by dissolving the fat in a good grade of gasoline using
from four to five ounces of gasoline and repeating the extraction at
least twice. After the gasoline is added to the fat, salt and curd, the
whole is thoroughly mixed with a small glass stirring rod and then al-
lowed to come to rest and stand for about two minutes during which
time the salt and curd settle to the bottom of the dish. The gasoline
with the fat in solution can then be carefully poured off from the res-
idue consisting of salt and curd. The salt and curd is then again
washed using the same amount of gasoline and allowing the mixture
to stand, pouring off in the same manner as above described, care being
taken of course to see that no curd is poured of with the gasoline.
There will be little likelihood of salt being poured off because of its
being heavy and therefore settling readily to the bottom of the dish .
and adhering to It. A few minutes are allowed for -the gasoline to
evaporate and then the residue of salt and curd is carefully heated
over a flame as in the moisture test. After cooling for a few minutes
the salt and curd is weighed. The fat determinations made by Mr.
Kohman's method compare very favorably with the results obtained by
the official method. Petroleum ether is the low boiling point fraction