ISS REPORTS ON TriE STAtE OF SCIEliTCiE. 



cau be obtaiiaed, however, by studying the efiect of adding to the solvent 

 known quantities of a pure substance of allied structure. Experiments 

 have been made on the influence of glucose on the solubility of 

 galactose, by Mr. Robertson on the influence of ^-mcthylglucoside on the 

 solubility of the d-glucoside, on the influence of ajr-dibromocamphor on the 

 solubility of the aTr-isomeridc and of bromocamplior Tr-sulphonamide on 

 that of the ^-sulphonamide : these have shown that in the case of sparingly 

 soluble compounds of high melting-point the change of solubility is 

 insigniticant. In the case of soluble compounds of low melting-point the 

 effects produced are no longer negligible, but the correction to be applied 

 may be estimated by similar methods. In the most extreme case that has 

 yet been examined the correction amounts to 2 per cent, on the volume 

 concentration or -t per cent, on the weight concentration. 



Since the appearance of the last report four investigations dealing 

 with the subject have been completed and described ; briefly summarised, 

 the results obtained are as follows : — 



1. Nitro-derivatives of Camjihor.^ — The solubility of normal nitro- 

 camphor in light petroleum increases in the course of a few hours in the 

 ratio 082 : 1, indicating that when equilibi-ium is attained the normal 

 and pscudo forms are present in the ratio 82 •, 18 or 5:1 approximately. 

 Tn the case of the a--bromo dei'ivativc, the pseudo-form is that which 

 persists in contact with the solution : its solubility increases in the ratio 

 0'17 : 1; the isomerides are therefore present in the ratio 83 : 17 or (as 

 in the case of nitrocamphur itself) 5 : 1 approximately. 



2. Glucose and (J alactose.' —In metliyl-alcoholic solutions one half of 

 the sugar is in the a-form, the other lialf probably consisting almost 

 entirely of the stereoisomeric y8-sugar. In presence of water the proportion 

 of (he a-sugar decreases : this might be due to a displacement of the 

 equilibrium between the a and ^ sugars but is more probably due to the 

 formation of a largely increased proportion of a third form of the sugar, 

 such as the aldehyde or its hydrate. The foi-mation of some such inter- 

 mediate compound in M'hich the terminal carbon atom is no longer 

 asymmetric appears to be essential to account for the optical inversion 

 which accompanies the interconversion of the o and /? sugars. 



3. Brumocam2)hor and Cldwocaniphor.^ — Kipping has shown ' that 

 these compounds, although stable in neutral solutions, undergo rcvcrsibh! 

 isomeric change in presence of alkalies. This change is accompanied by 

 an increase of solubility in the ratio 089 ; 1 ; a similar increase is 

 observed in the case of the /3 and k bromo-derivatives of these compounds. 

 In the case of chlorocamphor and bromocamplior the proportions of the 

 f(-compounds in the solutions arc probaljly somewhat greater tli.ui 89 per 

 cent, owing to the influence of the a'-compound in increasing (he 

 solubility of the a-compounds. The proportions arc estimated at 91 per 

 cent, and 93 per cent, respectively. 



4. Sidphonir Derivatives of C'ainplior.^ — Kipping has shown '' that the 

 TT-sulphonic salts deri\ed frum a-bromocaniphor and a-chlurocaniphor 

 undergo reversible isomeric change in presence of a trace of free alkali, 

 Solubility measurements indicate that similar changes take place in 

 the case of the ^-sulphonic salts, amides and other derivatives but 

 the observations are complicated by the fact that the compounds of the 



' Lowry and Robertson, Tram., 1904, 85, 1541-1550. 



' Lowry, Trans., 1904, 85, 1551-1570. " Lowry, Trans., 1906, 89. 



♦ Proc, 1905, 21, 125. » Lowry and Magson, Trans., 1906, 89. 



« rroc, 1905, 21, 124. 



