1813.] On the Composition of Oxide of Zinc. 411 



By 1st experiment, of 74*564 acid -f 15-436 water 



2d 75-813 + 14-187 



3d 74-910 + 1 5-090 



Mean 75-096 + 14-904 



1 may remark here, that this result almost exactly coincides 

 with the table of the strength of sulphuric acid published by 

 Mr. Dalton (New System of Chemistry, part ii. p. 404); for 

 by that table we see that acid of the specific gravity 1*838 con- 

 tains 75 per cent, of real sulphuric acid. Now the acid which 

 I used was of the specific gravity 1-8399, and contained 75*096 

 per cent, of real acid. 



2. I diluted 1004 grains of this acid with water, and put into 

 it a plate of zinc. The acid was allowed to act upon the zinc for 

 21 hours. It then had lost the power of reddening paper stained 

 with litmus. Hence I considered it as neutralized' The quan- 

 tity of zinc dissolved was 62*7 grains. The experiment was 

 repeated with the same weight of acid, and the zinc was allowed 

 to remain in the liquid for two days. The quantity dissolved was 

 62-93 grains. Supposing it possible that some portion of the 

 acid might remain uncombincd with the oxide of zinc for want 

 of time, I repeated the experiment a third time: 100 06 grains 

 of acid were diluted with water, and a plate of zinc of consider- 

 able size was kept in it for nine days, the liquid being frequently 

 agitated, and the zinc brought in contact with every part of it. 

 The portion of zinc dissolved in this case was only 61*5739 

 grains. 



According to these experiments, 100 grains of real sulphuric 

 acid dissolve 



By 1st experiment 83-16S grains of zinc 



2d 83-165 



3d 81-944 



Mean 82-859 



3. I consider it as established by experiment that 100 parts of 

 pure sulphuric acid are neutralized by a quantity of base, which 

 contains 20-02 of oxygen. Thus, for example, 100 sulphuric 

 acid combine with 280 of yellow oxide of lead ; and 280 of this 

 oxide contain 20 02 of oxygen. So, likewise, 100 of sulphuric 

 acid combine with 100 of black oxide of copper, which contain 

 20 of oxygen. It follows from this, since zinc has the property 

 of precipitating copper from sulphuric acid, and taking its place, 

 that the 82*859 of zinc which unite with 100 of sulphuric acid 

 must previously combine with 20-02 of oxygen. Therefore 100 

 sulphuric acid combine with 102-^79 of oxide of zinc; and the 



