310 PROCEEDINGS OF THE AMERICAN ACADEMY. 



there seems, however, to be little chance of reconciling it with his later 

 "corrected" values. 58 This is an example of the uncertainty that 

 seems to characterize the whole subject of polymerization in liquids, 

 especially on its quantitative side. 



The equation of the mean diameter which has just been obtained 

 can also be used for the computation of a rough but useful extension of 

 certain columns of the ordinary steam tables up to the critical point. 

 As was mentioned on page 306, the extrapolation formula for L of Sec- 

 tion 3 determines the change of volume during evaporation at all tem- 

 peratures between 320° and the critical temperature. From these and 

 the mean densities given by the equation of the diameter, it is easy to 

 compute each of the densities separately, and to fill in the rest of the 

 steam dome on the t s (temperature-density) planes. The results are 

 shown by the dotted lines in Figure 16, and are given in detail at the 

 end of Table I in the Steam Tables already mentioned. Any values 

 obtained in this way are, of course, only rough approximations to the 

 truth and should not be too much relied on. 



Summary of the Results in this Paper. 



1. It presents a new set of values for the difference between the 

 total heat of saturated steam at certain temperatures between 65° and 

 190°C. and its value at 100°. 



2. It shows that these differences can be represented within their 

 limit of error by the first three terms of a Taylor's series, but that such 

 a development should not be extrapolated far in either direction. The 

 best direct measurements of H indicate that its value at 100° is 639.11 

 mean calories. If this be accepted, the proposed formula for H is 



H = 639.11 + 0.3745 (t — 100) — 0.000990 (t — 100) 2 mean calories. 



The last two terms of the formula are the real contribution of this 

 paper, and may still be valid, even if the first term is later found to be 

 wrong. 



3. Thiesen's formula for L with recomputed constants is shown to 

 represent satisfactorily all of the reliable values of L, including those 

 in this paper. It is believed to be the safest known means of extrapo- 

 lating to high temperatures. 



4. The literature on the specific heat of superheated steam is sys- 

 tematically discussed and revised in the light of the new values of H 



68 Third paper; Proe. Roy. Soc., 1894, 56, 171; translated in Zeitsch. 

 Phys. Chem., 1894, 15, 106. 



