Reynolds — Report on Glucinum. 



733 



cation to enable us to found upon it a plan for the determination of 

 the atomic weight so called of a particular element : for it is evident 

 that if we employ as a standard a metal whose atomic weight and 

 specific heat are both accurately known — silver for example (= 108) — 

 the weight of another solid element which contains the same quantity 

 of heat at 100° C. as 108 parts of pure silver at 100° C. is the atomic 

 weight of the element. In seeking to compare glucinum with pure me- 

 tallic silver in this way, I succeeded in arranging an experimental 

 method which not only enabled me to attain the object I had in view, 

 but also to demonstrate the truth of the law just referred to. The appa- 

 ratus required is easily constructed, and consists of a spirit thermometer 

 with a cylindrical "bulb" in which a test tube is sealed after the manner 

 of Bunsen's ice calorimeter. This part of the apparatus is easily con- 

 structed from a small chloride of calcium drying tower as shown in the 

 diagram. Although the larger " bulb " of the thermometer is filled with 



spirit, the lower one and the stem are full of mercury, and connected 

 with a fine capillary tube carefully graduated in millimetres, and cali- 

 brated. The arrangement constitutes an exceedingly delicate spirit 

 thermometer, with a mercury index. 



When it is desired to compare a solid element with silver, in order 

 to fix the atomic weight, it is necessary to make a preliminary experi- 

 ment with the standard metal. Por this purpose one cubic centimetre 

 of distilled water is placed in the test tube which is immersed in the 

 bulb of the thermometer, and when the temperature has been equal- 

 ised, and the thread of mercury has reached a suitable position in the 



