SOL 
contained only 0.1 or 0.2°/, NH,Clor NH,Br. Thermal experiments 
yielded the limits — 20° and — 14° for the transition point. To 
bring these limits closer together I have examined whether a small 
quantity of water is a suitable catalyzer. I have succeeded in reducing 
the limits to —17.2 and — 15.6. From these experiments I have, 
therefore, to conclude to a transition point at — 16°, a value, 
which can depart a degree from the accurate one. The eutectic 
point Ni,[—H,O lies at — 28°; I have been able to observe both 
the occurrence of the eutectic point and of the transition point in 
one curve of cooling. 
I have not yet had an opportunity to determine the transition 
point more accurately. In the cited paper by Smita and EAsTLACK 
there have been recorded determinations of the solubility of ammo- 
nium iodide; the lowest temperature already lies below the transi- 
tion point. When these determinations of the solubility are continued 
towards lower temperatures the break will undoubtedly be clearly 
perceptible and the value can be determined with greater accuracy 
than has taken place above by the aid of thermal experiments. 
20. Summary of the results. 
The ammonium halides NH,Cl, NH,Br, and NH,I can all occur 
in two modifications. The transition points of the two first lie above, 
that of the third below the ordinary temperature of the room. At 
the ordinary temperature «-NH,Cl and e«-NH,br are isomorphous ; 
3-NH,I is, however, not continuously miscible with the two others. 
By the a-form the form is indicated that is stable below, by the 
B-form the form that is stable above the transition point. The sup- 
position suggests itself that the «-forms are continuously miscible 
inter se, and likewise the 2-forms, but that between «- and g-forms 
incomplete mixing always takes place. The succession of the transi- 
tion points NH,Cl 184.5°, NH,Br 137.4° and NH,I — 16° is that 
which would be expected according to the periodic system. 
Posteript during the correction: In Proc. Amer. Acad. of Arts and 
Sciences 52 91 et seq. (1916) Bripeman calculates from observations 
at high pressure that the transition points of NH,Cl, NH,Br and 
NH,I at ordinary pressure must lie at 184.3°, 137.8°, and — 17.6°. 
The first two deviate but little from my determinations ; the third 
value may point to this that the transition point lies at the lower 
limit of my thermal determinations. 
