( 336 ) 



under about the same conditions. They represent the averages of 

 resp. 2, 2 and 1 series. 



The meaning of those vahies for a is : When a current of one 

 ampère passes through a column of mercur^^ the TnoMsoN-effect will 

 cause a quantity of heat, equal ((► ö (expressed in gram-calories) to 

 be developed in one second between two consecutive sections of the 

 temperatures t — è° ^^"d t + 2°, if t^ie current goes in the direction of 

 the increasing temperatures. 



As the diagram added shows, the values I and II for lie all but 

 in straight lines, passing through the origin, whicli means, that the 

 TnoMsoN-effect is proportional to the absolute temperature (T). 



The values II give 7^ = — 284 X 10'^', ^^^^^ the combination of 



I and II give ^— 267 X lO-^. 



It is not clear what has caused the dilTerence between I and II. 

 May be it is the effect of some difference in purity of the mercury 

 which is known by experiments on other substances to strongly 

 affect the TaoMSON-constant. 



Chemistry. — Prof. Fkanchimont presents a communication from 

 Dr. D. MoL on an investigation commenced in 1903 as to 



the "ester anltydrides of dibasic acids. '' 



Of the anhydrides of organic dibasic acids but very little is known ; 

 only the internal anhydrides, which cannot be formed except in 

 those cases where the position of the two carboxyl groups in the 

 molecule is stated to be favourable, have been investigated. But in 

 some cases at least we may expect others formed in the same manner 

 as those of the monobasic acids, namely by the co-operation of two 

 molecules instead of the exercise of the two functions of the same 

 molecule. 



We may equally expect that when the dibasic acid has passed 

 into a monobasic one, for instance by changing one of the acid 

 functions into an ester or a salt, this will anyway yield an anhydride 

 in the same manner as other monobasic acids. 



Of some mixed anhydrides which are also esters we know, for 

 instance, the ethyloxalylchloride but not the simple anhydrides. 

 One of the chief methods of preparing the simple anhydrides is the 

 one applied by Gerhardt in 1853, namely, the action of acid 

 chlorides (mixed anhydrides) on salts. It is this method which, at 

 any rate with oxalic acid, has at once yielded the desired product. 



