87 
of Edinburgh, Session 1878-79. 
proved Millar-Casella thermometers for the bulk of the work, and 
the mercury piezometer and the inverting thermometer for particular 
cases. 
All the thermometers, of whatever type, should be carefully com- 
pared with a good standard and the results stated in terms of its 
scale. 
4. Preliminary Note on a Crystalline Compound formed 
in Water containing Sulphuretted Hydrogen and Mer- 
captan in Solution. By J. Adrian Blaikie, B.Sc. 
In the process of making mercaptan by collecting the distillate 
from a mixture of ethyl-sulphate of calcium and sulphydrate of 
potassium, along with water and mercaptan, a considerable quantity 
of crystalline substance was observed to collect in the receiver, and also 
towards the end of the condenser. The receiver having been placed 
in a freezing mixture, to condense as much mercaptan as possible, it 
was thought that the crystalline substance was ice, and the freezing 
mixture was removed. The crystals, however, continued to be 
formed, and even stopped up the end of the condenser, so that it 
was necessary to pour in hot water to melt them. In a few minutes 
they were again formed, not only in the receiver, but half way up 
the condensing tubes, through which water at about 2-3° C. was 
running. As it was evident that these crystals could not be ice, the 
conditions under which they were formed, and their composition, 
were subjected to investigation. 
The solution of sulphydrate of potassium having been completely 
saturated with sulphuretted hydrogen at a low temperature, a consider- 
able quantity of that gas was evolved before the formation of mercap- 
tan took place. ■ The crystals were therefore formed in an atmosphere 
of sulphuretted hydrogen, and as only water and mercaptan were 
present, could consist of water combined either with one or with 
both of the other substances. 
By pouring a few drops of mercaptan into sulphuretted hydrogen 
water at 0°C., immediately a few crystals were formed. By passing 
sulphuretted hydrogen gas into water saturated with mercaptan, and 
with mercaptan floating on the surface, in a few minutes crystallisa- 
tion took place, a large amount of sulphuretted hydrogen was absorbed. 
