SPECIFIC GEAVITY AND DISPLACEMENT OF SOME SALINE SOLUTIONS. 219 



In the followiug table we have in the first line the values of MR, in the second and 

 third lines the molecular displacements MRO3/D and MR/D respectively, in the fourth 

 line their differences, in the fifth line their ratios, and in the sixth line the corresponding 

 ratios MRO3/MR of their molecular weights. 



Salt. 



MR = 



MRO3 

 D 



ME 



D 



MRO3 MR 



D D 



MRO, /MR 



D 

 MRO 



mr" 



/MR 

 / D 



KCl. 



KBr. 



KI. 



RbCl. 



RbBi. 



Rbl. 



52-86 



51-88 



54-60 



53-31 



58-00 



60-07 



38-23 



44-46 



54-58 



44-71 



51-55 



61-99 



14-63 



7-42 



0-02 



8-60 



6-45 



-1-92 



1-38 



1-17 



1-00 



1-19 



1-12 



0-97 



1-64 



1-40 



1-28 



1-39 



1-29 



1-41 



CsCl. 



60-44 63-52 



CsBr. 



Csl. 



42-31 



18-13 



1-43 



1-28 



47-82 



15-70 



1-33 



1-22 



63-52 



57-67 



5-85 



I-IO 



1-18 



§ 138. Concluding Remm'ks. — These will be very short. The paper has already 

 expanded to an unexpected length, and yet, owing to the enormous amount of ex- 

 perimentally established material, the discussion of it which has been possible is far 

 from adequate, but an end must be made somewhere. 



The Table of Contents has been drawn up in a form which constitutes it really a 

 recapitulation of the principal features of the paper, with reference to the paragraph and 

 page where they are to be found, so that the reader has no difficulty in making himself 

 acquainted with the matters dealt with in the paper, or in studying those which more 

 particularly interest him. This being so, I will content myself by indicating here the 

 points about the research which present the greatest interest or novelty. 



Two methods of determining specific gravities are used. Neither of them is new in 

 principle, but there are innovations in the details of both. To take the case of the 

 determination of the specific gravity of a soluble salt in its own mother-liquor, the 

 principle is not new, because, if the common practice of determining the specific gravity 

 of a salt in petroleum is adopted, the liquid in which it is weighed is, or ought to be, 

 a saturated solution of the salt from which, as a mother-liquor, crystals of the salt can 

 be obtained ; but it is obvious that this is a very different case from determining the 

 specific gravity of chloride of caesium in its mother-liquor, which contains in solution 

 something like two parts of salt to one part of water. To carry out correctly this opera- 

 tion, the experimenter must be a trained and very experienced chemist ; but it is not 

 necessary to be an experienced chemist to perceive the experimental difficulties of the 

 operation ; it is therefore unlikely to be attempted by unsuitable hands. 



The principal method used, namely, that in which the very ancient instrument, the 

 hydrometer, is used, also requires to be practised by a trained and experienced chemist 

 if it is proposed to obtain results of the exactness recorded in this memoir. But to most 



