1897-98.] Dr A. Galt on Heat of Combination of Metals. 141 
taken by the aid of a magnifying glass. The bulb was now quickly 
plunged to near the bottom of the flask by pushing the glass tube to 
which it was sealed down through the cork, its descent being limited 
by the knob on the tube. If the method of pouring the acid on the 
filings or of dropping the filings into the acid had been adopted, a 
violent action would have occurred and it would not have been 
possible to prevent the loss of heat due to escape of fumes. But the 
plan adopted effectually got rid of this difficulty by the almost 
instantaneous, projection of the bulb containing the filings to the 
bottom of the acid.* It was very interesting to observe the scour- 
ing effect in the bulb due to the chemical action ; the filings were 
almost instantly expelled from it by the rapid evolution of gas, the 
removal being facilitated by the existence of the tw T o apertures 
already described. The gentle rotatory motion given to the acid 
was kept up while solution was going on, and when it was com- 
plete the thermometer reading was again noted. The time required 
to effect solution was 50 to 55 seconds, and it was observed that 
complete solution and maximum temperature were reached about 
the same time. The total weight of the whole apparatus — flask, 
cork, thermometer, and glass tube with attached bulb, but without 
metals and acid — was 20 '5 grammes, and its water equivalent was 
taken as 3*5 grammes. The tabular statement below gives some of 
the latest results obtained on 29th January last. 
* Andrews’ Scientific Papers, p. 214. “Every chemist is familiar with the 
violent action of nitric acid on zinc and copper, and the abundant evolution 
of gas which accompanies it. But the facility with which the gases may be 
condensed by the acid solution is probably not so generally known, and when 
the experiment is made for the first time it cannot fail to excite surprise.’’ 
[Tabular Statement. 
