104 
PROFESSOR W. RAMSAY AND DR. S. YOUNG 
present, and is capable of being altered at will, and as the number of experiments 
made on this subject comprise several thousand readings, and lasted over six weeks, 
we content ourselves with reproducing the results in the form of curves. (See Plate 2.) 
It may be generally stated that the larger the amount of substance the higher the 
pressure at which the double flexure appears. It may possibly be that succinic acid 
has the power of forming intermediate anhydrides of some such type as 
p T=r /COOH 
°a tl 4\CO\ n 
WtPxcoOH 
and that its abnormal behaviour is to be accounted for on the supposition of their 
existence, but this is merely a conjecture. 
§ 57. Temperatures of Volatilization of Succinic Acid. 
The bulb of the thermometer was dipped repeatedly into the melted acid until a 
sufficiently thick layer had accumulated. For low pressures the condenser was cooled 
by a freezing mixture, and the tube was jacketed with vapour of methyl salicylate. 
Series I. 
Pressure. 
Temperature. 
millims. 
0'9 
1587 
2-8 
166-8 
2*5 
169-3 
Series II. 
Pressure. 
Temperature. 
Pressure. 
Temperature. 
Pressure. 
Temperature. 
millims. 
millims. 
millims. 
155 
160-7 
6"4 
174-7 
75'4 
1751 
1-65 
161-5 
7-4 
176-0 
107-8 
174-3 
1-70 
161-0 
12-5 
176-8 
139-3 
1741 
1-90 
162-4 
15-6 
1761 
168-7 
174-2 
2-1 
162-4 
17-1 
176-5 
220-4 
174-5 
30 
167-3 
30-9 
175-6 
275-1 
174-5 
4-3 
170-2 
51-1 
175-8 
The substance meited after the pressure had been raised to 275‘1 millims.; the 
melting-pressure must therefore occur between the pressures 220‘4 and 275'1 millims. 
After the experiments were finished the melting-point of the acid still adhering to the 
thermometer bulb was compared with that of the original substance, and they were 
