452 



Dr. J. J. Hood on Retardation 



Table I. 



Salt, 



/. 





Time to oxidize 



2 grams. 



9- 



iron from y to?/'. 



Blank 



1158 

 156-2 



77-2 

 105-0 



100-0 

 134-8 



Am 2 S0 4 



K 2 S0 4 



1559 



104-4 



134-6 



Na 2 S0 4 



1554 



104-2 



134-2 



Li 2 S0 4 



1553 



103-4 



134-1 



MgS0 4 



148-7 



99-2 



128-4 



ZnS0 4 



141-3 



941 



1220 



CdSOi 



132-1 



88-2 



114-0 



The noteworthy points exhibited by these numbers are 

 that equal weights of the sulphates of ammonium, sodium, 

 potassium, and lithium produce equal retardation-effects of 

 approximately 17*2 per cent per gram ; whereas the sulphates 

 of zinc, cadmium, and magnesium, metals usually grouped 

 together in the same sense as the alkali ones, all produce 

 different effects. If the percentage retardation produced by 

 one gram of a salt be defined as its retardation-coefficient, the 

 values for the above salts are, for the alkali group, 17*2 ; for 

 ZnS0 4 , 11 ; CdS0 4 , 7 ; and for MgSO„ 14-2. 



The study of the influence of heat on the values of these 

 retardation-coefficients it was considered would be of interest, 

 in view of the general hypothesis regarding the intermolecular 

 motions that take place in a chemical system, as well as the 

 accelerating effect of heat upon these movements. 



The numbers that are given in Table II. relate to MgS0 4 , 

 and are selected from a considerable number of experiments 

 in which various sulphates were employed ; but the facts 

 brought to light were all of the same general character as 

 with MgS0 4 . 



In these experiments, instead of 2 J molecules of chlorate 

 only \\ was used, the equation representing the experiments 

 being consequently 



/Ai.jmi y + 5-25 rl v + 46-46\ 

 /^4-42olog 10 ^— . 5 log 10 ^- )= 9 + t. 



