ACCURACY OF NEUMANN’S METHOD. 79 
as the variations shown by the duplicate analyses given in 
Table I were no less than those shown by the analyses 
performed as described above, Neumann’s proportions were 
reverted to. The values given are the amounts of P,O; in 
10 ce. of milk. 
Table I. 
Amounts of P,O; found in 10 cc. of milk by Gregersen’s modifica- 
cation of Neumann’s method. 
Estimation. Result A. Result B. Difference. 
i 24°9 mg. 23°1 mg. 1°8 mg. 
vy oN x. OOP as OS eet 
3 25°8 ,, 2 Olea 0:3"; 
4 22:4 ,, De ae 0-2 
The maximum difference between any two of the results 
shown on this table is 1°8 mg.; the average difference 
between two estimations is 0°9 mg. (Compare with 
Table II.) 
In the series of estimations on standard phosphate solu- 
tions the method of transferring the small amount of 
precipitate on the filter to the flask was different; the 
precipitate was dissolved out with 60 cc. of 1:3 ammonia, 
and the filter then washed ammonia free, the washings 
being added to the flask; the ammonia is all got rid of again 
jn the subsequent boiling with caustic soda. This procedure 
makes the titration rather easier, as a large amount of 
filter paper in the solution is apt to obscure the end-point. 
Results. 
(a) Milk.—The following are some of the results obtained 
in the analysis of milk, illustrating the very variable close- 
ness of agreement between the duplicate analyses. The 
figures represent the amount of P.O; in 10 cc. of whole 
milk. 
