218 MR J. Y. BUCHANAN ON THE 



§ 134. In sub-table (j) is given the molecular displacement, MRO3/D, of the crystal 

 in grams of water, and in sub-table {m) the same constant MRO3/I8D is given in 

 molecules of water. 



In the potassium salts the values of this constant is least for KBrOg, and greatest 

 for KIO3. In the rubidium salts there is a progressive increase from the chlorate to 

 the bromate and the iodate. In the caesium salts the values for the bromate and iodate 

 are identical, and that for the chlorate is only very little lower. 



§ 135. Sub-tables (d), (e), and {/) give the concentration of the mother-liquor for each 

 salt, expressed in three different ways. In (e) it is expressed in gram-molecules, m, of 

 salt per 1000 grams of water, and for none of them is the value of m as high as 0*5. 

 Therefore, although saturated, they cannot be called concentrated or strong solutions. 

 As was pointed out in § 132, these values of the concentration of the mother- liquor 

 are derived from its specific gravity by extrapolation from the ratios of concentration to 

 specific gravity in the most concentrated solutions of the salts, as given in § 26, Tables 

 16 to 24. This course was adopted owing to the difficulty of determining analytically 

 the concentration of solutions of the salts of the ennead MRO3 and the uncertainty of 

 the results obtained by desiccation. The dependence of the value of the concentration 

 on that of the specific gravity of the mother-liquor excludes certain lines of discussion 

 which were followed in the case of the solutions of the salts of the ennead MR. 



It will be remarked that the specific gravities of the non-saturated solutions were 

 all determined at Id'd" C, and are referred to that of distilled water at the same 

 temperature as unity, while those of the mother-liquors are determined at temperatures 

 inferior to 19*5° C, but the specific gravity of each solution is referred to that of 

 distilled water of the same temperature as unity. This almost completely eliminates 

 any error in the determination of the concentration of the solution which might accrue 

 from the difference of temperature at which the specific gravities were determined. If 

 Table 66 in § 28 be referred to, the value of possible error due to this cause can be 

 ascertained for the two temperatures 19 '5° and 23° C. The concentration of the 

 KCIO3 solution would be given too low by 2 per cent. ; in the case of the other solutions 

 the error would be less than 1 per cent. But the specific gravities of the mother- 

 liquors were determined at temperature lower than 19*5°, and the error would be less 

 and in the opposite sense. 



5 136. In sub-table (m) we have the vakies of — ^^ . They are all positive; 



Dm' 



therefore in every case crystallisation is accompanied by expansion. This is small in 



the case of RbClOs and CsClOg, considerable in that of KCIO3 and the bromates, and 



very high in that of the iodates. It is remarkable that the crystallisation of each of 



the three iodates is accompanied by identical expansion. 



§ 187. Finally, attention must be called to the efi"ect on the molecular displacement 



in crystal of the salts of the ennead MR by the addition of O3 so as to form the 



corresponding salts of the ennead MRO3. 



