AND TIIH RELATION OF Sl'KCIFIC HEAT TO ATOMIC WKKMIT. 



247 



t arc of solid carbon dioxide, which was taken as 78'4, and again at the temperature 

 of tailing oxygen taken as 182 '5. 



For this purpose a thin brass cylindrical vessel holding 400 c.c. of water, provided 

 with an efficient stirrer in the form of a horizontal brass plate, perforated with rather 

 l.-irge holes, was used. This calorimeter was supported by silk cords within a bright 

 tin double-walled cylinder, the annular space being filled with water. The top of 

 the tin casing was covered by asbestos card to prevent air currents, but arranged so 

 as to allow the passage of the thermometer and the silk cord carrying the stirrer. 

 The thermometer was divided into large tenths of a degree, and could easily be read 

 to *01. The zero had been verified by ourselves, and it had been compared with a 

 standard at Kew at each degree, the correction to the nearest '01 being supplied. 

 So far as the observations of temperature in the calorimeter, the determination of the 

 mass of water used and of the water equivalents of the brass, the thermometer, <kc., 

 were concerned, the usual procedure was adopted, and no details are necessary. 



The problem of how to convey the cooled metal into the water of the calorimeter 

 without appreciable heating in the air required a special contrivance. This is 

 represented in the accompanying figure. The metal for experi- 

 ment was placed in the interior, c, of a double brass tube, a, so 

 constructed that the spice, d, between the inner and outer tubes 

 will hold liquid. The top of the inner tube, shown by the dotted 

 line, is closed, while the top of the outer tube is open. The rod, 6, 

 by which the tube is held, is extended into a long wooden handle. 

 The metal is retained in its place within c by means of a brass plate, e, 

 working smoothly upon the mouth of the tube which it closes, and 

 capable of being turned aside by rotating the head,^ of the rod 

 which is attached to it at one side. The metal being introduced 

 and supported by e, the holder was gradually plunged into liquid 

 oxygen contained in a large cylindrical vacuum vessel till the 

 double brass tube was completely immersed and the space, d, filled 

 with liquid. The whole was left in the liquid till ebullition had 

 practically ceased, or was proceeding at the same slow rate as the 

 oxygen in a second vessel kept for comparison alongside. This 

 happened in about 10 minutes after immersion. The metal was 

 then assumed to be at 182 '5 very nearly. On lifting out the 

 brass holder the annular space between the two tubes remained 

 full of liquid by which the temperature of the whole was kept 

 down, and bringing the tube over the water in the calorimeter, 

 the dish f was turned and the metal fell into the water. 



The cold tube when brought into the air is of course attended 

 by a cloud of cold air and mist which flows downward. In order 

 to prevent the entrance of this mist into the calorimeter or its water- jacketed case a 



