338 
without passing the limit for pure butters. It is evident 
that this last amount might be doubled with a butter giving 
the extreme value. 
Range for genuine butters. Adnlteration pos” 
ble withort deter: 
Method. Min. Max. Average. tion. Per cent, 
Reichert’s c.'c. +4 Na O H.. 12.5 16+ 14 10-- 
Insoluble acids, per cent..... 86.4 90.2 88.2 20+ 
Boluble acids, per cent...... 4, 6. Bip ie) 20 
Koetstoerter i. i. ait 221.1.) 223: 225. 12+ 
From the above scheme it is plain that Reichert’s process 
is capable of detecting a smaller proportion of adulteration 
than any of the others. 
Koettstoerfer’s method is simple in its details and would 
appear from this table to be capable of showing nearly as 
small a percentage of adulteration as Reichert’s, but the 
sources of error in it are large so that, in reality, more de- 
pendence may be placed upon determinations of the soluble 
and insoluble acids than upon this. 
These considerations have led to the quite general adop- 
tion of Reichert’s method by chemists whenever the quality 
“ 
of butter is to be determined. 
THE VISCOSITY OF BUTTER SOAPS. 
In making examinations of butter by Reichert’s method 
I have often observed a very marked difference in the solu- 
bility of the soaps formed from genuine and from adul- 
terated butters or other animal fats. While the potash 
soap from butter fats, made according to Reichert’s direc- 
tions, is readily soluble in 50 c.c. of water, that made from 
lard or oleo-oil, or from samples containing a large propor- 
tion of these oils can only be dissolved by warming, and the 
solutions when formed appear much more viscous than 
solutions of the butter soaps. This characteristic property 
is so marked that nearly all of the butterine and oleomar- 
garine butters may be detected by a simple inspection of 
these soap solutions without further tests. This fact sug- 
gested that perhaps the measurement of the viscosity of 
solutions of soaps made from the different fats and oils, 
might furnish a ready means for identifying them. 
To test this, a preliminary trial was made with neutral 
lard and butter fat. Twenty grams of each of these were 
saponified with about 10 grams of caustic potash by heating 
with a quantity of alcohol. No especial care was taken to 
have exact quantities either of potash or alcohol. The soaps 
formed were dissolved in water and the solutions made up 

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