ANALYTIC PROCESSES 27 
tin is a good material. Moerrs found that Jena- 
glass tubes resist the action of the ammonium 
hydroxid. Distillates should be titrated promptly 
as alkali may be dissolved from the glass. 
A satisfactory condensing arrangement for 
general laboratory use is a copper. tank of good 
size, through which several condensing tubes pass. 
Aldehyde Number.—The addition of formalde- 
hyde to milk increases the acidity by an action on 
the proteins. As commercial formaldehyde is 
always acid, the acidity must be either determined 
or neutralized in applying the following method. 
The application of the reaction to determination 
of proteins in milk is due to Steinegger. Rich- 
mond and Miller investigated the method and 
suggested the use of strontium hydroxid instead 
of sodium hydroxid. Richmond gives the 
following details: 
To ro cc. of milk at least 1 cc. of a 0.5% 
solution of phenolphthalein is added and the 
liquid neutralized with standard strontium hy- 
droxid solution. To the faintly pink liquid, 2 
c.c. or more of 40% formaldehyde solution are 
added and the titration made to the same tint 
as the former. The’strontium hydroxid required 
by the formaldehyde solution must be: known, 
and this being deducted from that which was 
used in the titration and the remainder calculated 
