Effect of Temperature, Acidity, etc. 



397 



Thus after one day's heating sulphur dioxide is formed if 

 the initial acid concentration reaches 1 per cent, and it appears 

 after a longer time where the acid is weaker. At no temper- 

 ature, however, do these side reactions appear to have any con- 

 nection with the crystalline form of the 'product. 



Table I. 

 The relation between the sulphide formed and the acid set free. 







Gain in wt. 



Gain in wt. 



Final acid 



Final acid 



Initial 



Tempera- 



FeS 2 



of acid calc. 



of acid 



in wt. % 



in wt. % 



acid 



ture 



found 



from FeS 2 



found 



calc. 



found 



inwt. % 



25° 



2*46 



2-01 



2-23 



0-115 



0-127 



0-015 



tt 



3*67 



3-00 



3-18 



•165 



•173 



•015 



(( 



4-31 



3-52 



351 



•235 



'234 



•059 



100° 



1-32 



1-08 



I'll 



1-54 



1-58 



o-io 



tt 



•93 



•76 



•73 



1-26 



1-22 



•25 



« 



•68 



•55 



•55 



1-23 



1-20 



•50 



a 



•43 



•35 



•37 



1-47 



1-50 



1-00 



u 



1-03 



•84 



•86 



2-62 



2*65 



1-50 



200° 



0-71 



0*58 



0-60 



1-27 



1-30 



0-50 



a 



•96 



•78 



•74 



2-04 



2-00 



1-00 



ft 



•96 



•78 



•75 



2-54 



2-49 



1-50 



tt 



•93 



•76 



•70 



3-01 



2-90 



2*50 



a 



•68 



•55 



•52 



3*24 



3-19 



2-50 



200° 



1-02 



0-83 



0-68 



2-10 



1-91 



1-00 



tt 



•82 



•67 



•49 



2-14 



1-90 



1-25 



« 



•81 



-6G 



•47 



2-64 



2-37 



1-75 



a 



•74 



•61 



•34 



2-81 



2*45 



2-00 



n 



•73 



•60 



•33 



3'30 



2-94 



2-50 



300° 



1-18 



0-95 



0-74 



1-36 



1-08 



o-io 



a 



1-04 



•85 



•61 



2-13 



1-82 



1-00 



tt 



•81 



•66 



•30 



2-89 



2-40 



2-00 



it 



•29 



•24 



•17 



3-32 



2-78 



3-00 



Table II. 



Neutralization of H 2 SOi by Jena combustion glass* at 200° 



Time = 3 days. 



Grams Grams H 2 S0 4 Grams Concentration Concentration 



H 2 S0 4 found after H 2 S0 4 H 2 S0 4 in wt. % H 2 S0 4 in wt. % 



taken heating neutralized before heating after heating 



0-1937 

 0-3874 

 0*2949 



0-1859 

 0-3752 



0-2875 



0-0078 

 0-0122 

 0-0074 



0-97< 



1-94 



2'95 



0-93^ 



* The surface exposed to the action of the acid was about 30 cm2 . 



