10 IOWA ACADEMY OF SCIENCES. 



Cu+H^SO.^Cu SO.+Hj [5 



2H+H,SO,=2H,0+S02 [6 



formiug water and sulphurous anhydride. 



Many other cases might be cited of simple reactions in which it is consid- 

 ered necessary by some authoi's to employ the nascent hypothesis, but I shall, 

 for the present, confine myself to these and in the light of the facts seek an 

 answer to our four crucial questions. If we dispense with the hypothesis 

 we must assume in each case a direct action of the metal on the salt; thus 

 zinc and ferric chloride would give zinc chloride and ferrous chloride. 



Zn+2Fe Cl3=Zn Cl2+2Fe Clj [7 



Zinc and copper sulphate would simply present a case of direct inter- 

 change of metals. 



Zn+Cu S04=Zn SO^+Cu [8 



The reduction of copper by electrolysis would be primary not secondary. 



To negative pole. To positive pole. 

 Cu < Cu SO. ^> SOg+O [9 



This yiew iu the latter case will not be seriously questioned by any stu- 

 dent of the recent work of Arrhenius and Ostwald and their followers. 



Lastly, we can simply represent the reduction of hot concentrated sul- 

 phuric acid as consisting in the first stage in an oxidation of the copper at 

 the expense of the acid. 



Cu+H,SO,=Cu 0+ B.2 SO3 

 H2O SO2 



The sulphurous acid becoming dehydrated of course at the high temper- 

 ature of the reaction; and the copper oxide being soon converted into copper 

 sulphate. 



In the cases named it is clear that the nascent state hypothesis is not nec- 

 essary and does not lead to a simpler explanation of the facts than can be 

 had without it. Is it inconsistent with any of the facts? Considering first 

 the reduction of sulphuric acid by copper, the following phenomena may be 

 observed: When metallic copper, carefully cleaned, is heated gradually with 

 concentrated sulphuric acid until sulphurous anhydride begins to be evolved, 

 the surface of the copper becomes coated with a black crust. If the metal 

 is nowi'emoved from the acid, then washed and placed in hydrochloric acid, 

 the coating dissolves, forming a solution of copper chloride. In fact, this 

 crust consists of copper oxide. Its formation is not explained by the hypoth- 

 esis in question (eqs. 5-6) but is a dii'ect confirmation of eq. 10. If the acid 

 is reduced by hydrogen some of the hydrogen might be expected to escape 

 unoxidized. In order to test this point pure sulphui'ic acid was heated with 

 copper which was obtained by electrolysis from a recrystalized specimen of 

 copper sulphate and subsequently ignited in an atmosphere of carbon monox- 

 ide. The gases evolved were collected over mercui-y and about 50 c. c. were 

 treated with caustic potash. All was absorbed except a small bubble, which 

 consisted essentially of oxygen. No hydrogen could be detected. 



In order to demonstrate, however, that none had been formed it was nec- 

 essary to show that if formed it would not be wholly oxidized by the hot 

 acid. To get direct evidence upon this point, a quantity of nearly pure 

 zinc was heated with the same acid that had served for the copper experi- 

 ment and in the same way. Fifty c. c. of the evolved gas was only partly 



