100 PROCEEDINGS OP SECTION B. 



Abegg (Zeit. phys. Chem., 1909, 69, 1) has already pointed out a 

 relation between the heat of hydration of basic oxides and the dis- 

 sociability of the product into ions. It appears possible, therefore, 

 that dissociability of product, heat of hydration of anhydride and rate 

 of hydration are in some way connected. 



As regards the mechanism of the hydration, the independence 

 of the velocity constant on initial concentration suggests that hydrogen 

 ion is not a catalyst, and that therefore the mechanism is different 

 from that of the nearest analogous case, the hydrolysis of esters. 

 Orton and Jones (Journ. Chem. Soc, 1912, 101, 1708), however, show 

 that in presence of mineral acids there is distinct acceleration, and 

 claim that this points to the same type of catalysis as is found with 

 esters. But as a matter of fact, the catalysis in aqueous solutions is 

 feeble, while in anhydrous solvents it may be very great. This suggests 

 then, that it is not always the hydrogen ion that acts as catalyst, but 

 that the undissociated molecule does so. It therefore seems to the 

 author still rather an open question as to whether the mechanism of 

 hydration of anhydrides is identical with that of the hydrolysis of 

 esters. For further investigation of the effect of mineral acids, the 

 conductivity method is not suitable. 



5.— THE SEPARATION OF IRON AND MANGANESE.* 

 F. H. Campbell, M.Sc. 



(Abstract.) 



A complete quantitative separation of iron from solutions con- 

 taining manganese can be brought about by the addition of a mixture 

 of potassium iodide and iodate dissolved in water. The iron is pre- 

 cipitated as a hydrated oxide uncontaminated by any trace of 

 manganese. 



6.— THE ESTIMATION OF CARBON DIOXIDE IN THE AIR.— 

 A SIMPLE AND EXPEDITIOUS METHOD. 



By W. M. Doherty, F.I.C., F.C.S., Government Laboratory, Sydney, 

 New South Wales. 



The rapid estimation of carbon dioxide in the air of rooms, public 

 halls, factories, or wherever numbers of persons congregate in confined 

 spaces, is sometimes very desirable. The older methods in use are 



* For full papsr, see Journ. Soc. Chem. Ind., 1912. 



