30 JOURNAI. OF THE 



ever. Not only copper sulphate, but cuprous sulphide 

 and sulphur dioxide had also formed. Copper, therefore, 

 decomposes concentrated sulphuric acid (sp. gr. 1.84) 

 practically at zero. 



Prom my own experiments and from experiments per- 

 formed with apparatus similar to that used by Andrews 

 and under the same conditions, except in regfard to the 

 important element, time, which consideration is necessary 

 for all chemical reactions, the author must adhere to his 

 f former statement. 



THE USE OP THE PERIODIC LAW IN 

 TEACHING. 



Read before Am. Asso. Adv. Science, Buffalo, August, 1896. 



Only a few years after the announcement of the period- 

 ic law, when as yet it had attracted little attention, Lo- 

 thar Meyer pleaded for its introduction by teachers of 

 Inorg-anic Chemistry so that something- of the orderliness 

 observed in org-anic chemistry mig^ht beg^iu to appear in 

 the study of the inorg-anic elements. A casual examina- 

 tion of the text-books of the period and indeed of those 

 for a number of years afterwards, would show the gfreat 

 need of some such system Ag-iiin the g-reat German 

 teacher twenty years later appeared before the Chemical 

 Society at Berlin and threw the weig-ht of the experi- 

 ence of these added years and all his enthusiasm in favor 

 of a thoroug-h use of the periodic system in teaching- in- 

 org-anic chemistr}^ 



Some system must be adopted in teaching- this branch 

 of chemistry or the task is hopeless. What will you use 

 if the periodic system is rejected? Some have answered 

 this by using- the old families where the elements are ar- 

 rang-ed by chemical analogies. Even in these families 



