46 



L. F. Nilson and Otto Pettersson. [Nov. 18, 



II. " On the Molecular Heat and Volume of the Rare Earths 

 and their Sulphates." By L. F. NlLSON and Otto 

 Pettersson. Communicated by Warren De La Rue, 

 D.C.L., F.R.S. Received June 21, 1880. 



At the request of the Royal Academy of Sciences at Stockholm, we 

 some years ago undertook an extended research into the physical pro- 

 perties of the rare earth-metals and their compounds. Having per- 

 formed the laborious task of separating and purifying their oxides, we 

 are now able to publish our first series of determinations concerning 

 their principal properties, which chemically are of the greatest im- 

 portance, viz., molecular heat and molecular volume. 



The rare earths, with a few exceptions (Ce0 3 , Th0 3 , Zr0 3 ), belong 

 co a group of sesquioxides. In order to obtain a larger number for 

 comparison, we have extended our research not only to the rare earths, 

 but also to some other nearly related compounds, the molecular heat 

 and volume of which were hitherto unknown. As to these values, 

 previously known for some other oxides, A1 2 3 , Fe 2 3 , Cr 2 3 , according 

 to Regnault, Kopp, and others, we have already observed in our pre- 

 ceding paper " On the Essential Properties and Chemical Character of 

 Beryllium," that only such determinations are strictly comparable 

 which are made by the same method, under the same circumstances, 

 and referred to the same unit of measure. 



The specific densities and molecular volumes, which are given in 

 the following tables, are obtained by means of a method, specially 

 adapted to prevent the errors arising from adhesion of air to pulve- 

 rulent substances.* The densities taken by this method will there- 

 fore generally be found a little higher and the molecular volumes a 

 little lower than the numbers usually given by others. 



The specific heats of the different compounds are determined with 

 Bunsen's ice-calorimeter, by means of the same process which we have 

 more fully described in our detailed memoir on beryllium. f All the 

 numbers given are the means of at least two determinations, which 

 agree perfectly, the experiments being made under the most favourable 

 circumstances. As to the values obtained, we beg to observe that the 

 specific and molecular heat will be found a little smaller by the ice- 

 melting method than by other methods, on account of the different 

 unit of comparison. 



The molecular weight of the different oxides was determined by a 

 special analysis or synthesis of the sulphates, and the very same chemi- 



* For the details, see Otto Pettersson, " Molecularrolumina einiger Reiken von 

 isomorphen Salzen," in " Not. Act. reg. Soc. Scient. Ups.," ser. iii. Upsala, 1873. 

 f " Pogg. Ann.," [2], iv, p. 554. 



