( 758 ) 
1.05 
temp. 15°. 
1.04: 
— 
S 
ee) 
"yyStem ‘oade 
= 
c=) 
w 
1.01 | 
a [ay ea 
not hydra Lome 
100 50 0 
N,H,.H,0 
1.90 
It will be seen that the system NoH,+ H.O behaves in an analogous 
manner to the system SO;+H,O which has been recently studied 
by Kyrerzscu in his well-known research on sulphuric acid. 
Here we also meet with contraction; there does not, however, 
exist a maximum density for SO;.H,O, (but for 2 SO,.H.O) which 
phenomenon may be explained by the great difference in density 
of the two components. 
Efforts will be made to determine the boiling point curve for the _ 
system N.H,+H.0 (or at least for NoH,.H,0+H,0). 
Chemistry. — ‘A method for separating crystals from alloys’. 
By Dr. C. van Eyk. (Communicated by Prof. H. W. BAKHUIs 
RoozrBoom). 
The following methods have, up to now, been applied in investi- 
gating the constitution and structure of metallie alloys. 
1. Mieroscopical examination of polished surfaces so as to distin- 
guish the several erystalline elements often rendered more conspicuous 
by etching (BEHRENS, OSMOND and others). 
Differentiation of crystalline elements presents as a rule no great 
difficulties but it is difficult to come to a proper conclusion as a 
quantitative analysis is seldom possible. In some cases it is possible 
