* 
tla = 
Re ey 
aoe ae rege nn ey 
3 oF vs + he hs a ” 
oT LE ee Y en we > a 5 
hea ry ci o. ; s 

No. 83.) -. mh eM 169 
In general, determinations by the two methods have agreed as well 
oet a other as would two. determinations made by the usual 
method. 
AS Hat: 
The tube containing the solids from five grams of milk, obtained as 
in the preceding section, is placed in a fat extractor and exhausted 
with ether in the manner described in the analysis of fodders. The 
fat is dried at 100° C. and weighed. The ether solutions ‘obtained in 
this way have all been clear. In more than a hundred determinations 
of fat in milk it has not been necessary to filter a single one before 
drying. 
5. Albuminoids — Casein and Albumen. 
The albuminoids and other constituents containing nitrogen have 
all been classed together under the head of casein. ‘The numbers 
given are obtained by multiplying the total nitrogen by 6.33. 
The total nitrogen is obtained from about five grams of milk. For 
this purpose the milk is weighed in the pipette, in the usual way, and 
run into an evaporator containing sufficient plaster of paris to absorb 
it. It is stirred for a few moments to prevent its hardening in lumps 
‘and placed for a short time in the drying oven. It is then pulverized 
in a mortar, mixed with soda lime and ignited in the usual way. Re- 
sults have been quite satisfactory. 
6. Sugar. 
Fifty c. c. of milk are run from a pipette into a 250 c.c¢. flask, di- 
luted with 150 c. c. of water and a few drops of acetic acid added. It 
is then heated on the steam bath nearly to 100° C. for a few moments 
to separate the casein and albumen. After cooling, the flask is filled 
to the mark and the contents filtered; 10 c. c. of the filtrate, equiva- 
lent to 2c. c. of milk are boiled with 50 c. c. of Fehling solution. The 
precipitated red oxide of copper is dissolved in an acid solution of 
ferric sulphate and titrated with a standard solution of potassium 
permanganate in the manner directed for the estimation of sugar in 
cane juice. A curve on the chart, described in the section on de- 
termination of sugar, represents the reducing power of milk sugar 
and shows directly from the quantity of potassium permanganate used 
the amount of sugar in two c. c. of milk. 
It is, however, sufficiently accurate in normal milk, if a complete 
analysis is made, to estimate the sugar by difference, as the following 
table shows. The figures given are not selected, but include every 
analysis made during the year in which all the constituents of the 
milk were determined. 
[Assem, Doc. No, 33. ] 22 
