8 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



IP^ 



and simple, its use introduces complications, because it must come in 

 contact only with a liquid that is an insulator. The water of the 

 preceding paper and nearly all the twelve liquids of this are not 

 insulators. Some auxiliary liquid must be used therefore, to transmit 

 pressure to the manganin coil. Kerosene has shown itself perfectly 

 adapted to the purpose, and has been used 

 in all this work. In the former work on 

 water, the kerosene and water could be al- 

 lowed to come directly in contact with each 

 other, but in this investigation, nearly all the 

 liquids are more or less miscible with kero- 

 sene, so that means had to be provided to 

 prevent the liquid under investigation from 

 coming into contact with the kerosene. This 

 necessitated slight changes in the design of 

 the apparatus, and the use of still a third 

 liquid, mercury, to keep the liquid and the 

 kerosene from direct contact. The modified 

 receptacle for holding the liquid is shown 

 in Figure 1. The liquid is enclosed in a steel 

 bulb A, the stem of which dips into the cup 

 B containing mercury. The cup B is bored 

 out at the lower end so as to protect the 

 manganin pressure gauge, which is shown at 

 C. The bulb, cup, and gauge together oc- 

 cupy the lower part of the pressure cylinder. 

 In order to obtain as large a quantity as 

 possible of the liquid to experiment on the 

 diameter of the bulb etc. was made larger 

 than that of the moving piston (|^ inch 

 against | inch). To allow this the cylinder 

 had to be bored out at the lower end to the 

 larger diameter. In other respects the cylin- 

 ,der is similar to that used for water, in fact it is the same cylinder, 

 the only change being the enlargement of the lower part to meet 

 the new requirements. 



The final form of receptacle shown in Figure 1 was arrived at only 

 after a considerable number of failures. Early attempts to use glass 

 cylinders, which from the point of view of purity would be more 

 desirable, had to be abandoned because of the invariable fracture of 

 the glass. This is doubtless because kerosene under pressure becomes 



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/ 



Figure. 1. The com- 

 pressibility bulb with 

 attachments. ^4 is the 

 bulb containing the liq- 

 uid under investigation, 

 B the mercury cup, and 

 C the insulating plug 

 and the manganin coil 

 with which pressure is 

 measured. 



