OF ARTS AND SCIENCES. 



321 



where /)' is the external pressure and T is temperature. In my 

 experiments, only a single value of volume is introduced, and hence 

 the work is not further available. Referring to the iutriusic equation 

 of Ramsay, Young, and Fitzgerald (loc. cit., p. 51), 



p'^RTl{v-v,)-iiiv\ 



so that here the internal pressure has the form p = fi/v\ 



11. Isothermals. — The question ceases to retain so simple an 

 aspect when the isothermals of liquids are considered. Of the two 

 equations which I discussed in my work * on the compressibility of 

 liquids, viz. : 



dp' 



d 



1 + ap' 



and 



dV 

 d^ 



fi 



(1 + vp') 



IV2 



• (6) 



where p' is the external pressure, and d, a, jW, v are constants, the 

 latter is at once compatible with the results of § 9. For equation (3) 

 leads to 



dV _ _ ^(T) 



dp p^ 



(7) 



and hence in equation (4), llv=p is the internal pressure active 

 under the isothermal circumstances of compression, and 



The results actually found for thymol are given in Table V., 2" being 

 the absolute temperature of the isothermals, and pressures being in 

 atmospheres. 



TABLE V. — Compressibility of Thymol, 



dV 

 dp 



nlv^ 



(l/r + /)2 



* Am. Journal, (3,) Vol. XXXIX. pp. 497 and 506, 1890. 



VOL. XXVI. (N. S. XVIII.) 21 



