334 REPORT OF THE CHEMIST OF THE 
INTRODUCTION. 
In 1892 there was worked out in the chemical laboratory 
of this Station a method for the determination of casein in 
cow’s milk.* This method, after careful trial by the Associa- 
tion of Official Agricultural Chemists, was adopted as “ offi- 
cial.”* It was realized that the method was adapted only for 
use in well equipped chemical laboratories and in the hands 
of trained chemists. Beginning 16 or 17 years ago, unSsUCccess- 
ful efforts were made here at different times to devise a simple, 
direct, volumetric method, requiring less apparatus, time, 
inanipulation and skill. Several attempts have been made by 
others to find such a method, among which we mention the 
following. (1) Estimation of casein: a preliminary study3 
(2) Quantitative estimation of casein.4 (3) A new method 
for the determination of casein.® These and other proposed 
methods are open to several practical objections. 
A method that is satisfactory in all respects for finding the 
amount of casein in milk should have the following character- 
istics: (1) It should be accurate; (2) its operation should 
require only a few minutes; (3) it should effect economy of 
time when several determinations are made at the same time; 
(4) the apparatus and materials used should be simple, readily 
obtainable and inexpensive; (5) the manipulations should be 
simple, such as can be acquired with a minimum amount of 
previous training; (6) the mechanical work required should 
not be needlessly tiresome. | 
In making a study of the accuracy of the results given by 
the method of Matthaiopoulos, it was found that a reconstruc- 

1N. Y. Agrl. Exp. Sta. Ann. Rept., 12:487-496 (1893); Jour. Amer. 
Chem. Soc., 15:635-645. 
U.S. Dept. Agr., Chem., Bul. 51. 
’V.H. Arny and T. M. Pratt. Amer. Jour. Pharm., 78:121-128 (1906). 
4T. B. Robertson. Jour. Biol. Chem., 2:328-334 (1906). 
5G. T. Matthaiopoulos. Ztschr. Analyt. Chem., 47:492-501 (1908). 
