322 Composition AND PROPERTIES OF MitK POWDERS 
point and held there for five minutes. ‘The water lost by evapora- 
tion was replaced. The hot solutions were then filtered and analyzed 
for total solids. 
The results of the above tests show that the spray-process 
powder when made from milk that was not heated above 150 de- 
grees F. before desiccation, had the power of returning into an 
emulsion in cold water that would filter in a similar manner and 
would pass through the filter with a similar degree of completeness 
as ordinary milk. The powder was substantially completely soluble. 
When made from milk that had been heated to the boiling point, 
the spray-process powder lost slightly over 10 per cent of its solu- 
bility. About one-half of this loss was recovered upon heating the 
water and powder mixture to the boiling point. 
The film-process powder in cold water went into a filterable 
emulsion to the extent of from 60 to 70 per cent of the powder 
added, and in hot water to the extent of from 78 to 80 per cent of 
the powder added. 
The very marked difference in solubility of the powders from 
the two processes could be readily observed also without chemical 
analysis. When the solutions of the film-process powders were 
allowed to remain at rest in test tubes there would always gather 
a very considerable deposit of solid matter in the bottom. This was 
the case in both hot and cold water, but the deposit was very con- 
siderably more voluminous in the cold mixture than in the hot 
mixture. 
In the case of the spray-process powders no such deposit of 
solid matter could be detected, neither in the hot nor in the cold 
mixtures. 
It is further interesting to note that the percentage of protein 
found in the filtrates from all the powders with the exception of 
the hot solution from the film-process cream powder, followed very 
closely the percentage of total solids in the same filtrates. This 
suggests very obviously that the degree to which the solubility, or 
better the power of the milk powder to return to the character of 
the original milk, is impaired by the process of desiccation, is largely 
controlled by and depends on the extent to which the process of 
desiccation changes the physical properties of the protein of milk. 
Miscibility and Readiness of Solution of Milk Powders.— 
The rapidity and readiness with which milk powders go into so- 
