ON SULPHUROUS ACID. 305 



ployed in the preceding experiments had equally the pro- action of the 

 perty here of reddening the sirup of violets, that had been 

 rendered blue by the sulphurous acid, and the following 

 were the results. 



■ With the nitric, muriatic, sulphuric, and phosphoric 

 acids, the blue liquor changed to a vinous red: 



With the acetic, to a light violet: 



With tlie oxalic, to a pale rose colour : 



With the tartarous, citric, and acetous, mixed in a very 

 large proportion, there was no tint of red, but a remark*, 

 able diminution of the intensity of the blue. 



Experiments with Sulphurous Acid Gas. 



Exp. 6. It is well known, that the sulphurous acid in Experiments 

 the state of gas acts with much more energy than in the Wlth the 6*** 

 liquid state. Accordingly I was desirous of examining its 

 action on sirup of violets, diluted as before, and changed 

 red hy the same acids. I disposed my apparatus exactly in 

 the same manner as for preparing sulphurous acid. As 

 soon as the seoond phial, three parts filled with distilled 

 water, was saturated, I opened a communication between 

 it and a third, filled with a mixture of water and sirup of 

 violets reddened by sulphuric acid. A few bubbles of the 

 sulphurous acid gas were sufficient to restore the blue colour 

 of the liquor. To this I substituted another phial, filled 

 with a similar mixture, except that it had been reddened by 

 a different acid : and thus I continued, till mixtures red- 

 dened by all the acids mentioned in the first experiment had 

 been subjected to the action of the gas. I did not observe It did not ap- 

 any very sensible difference between them ; but it appeared powJrfuny 1 " " 

 to me, that the colour was less weakened by tlie sulphurous 

 acid gas, than by the liquid sulphurous acid. 

 . The slight difference, however, may have depended on 

 the greater quantity of coloured liquor in the latter ex- 

 periments, and the facility with which the effects of the 

 gas could be observed, and its action governed. 



These experiments repeated with sulphurous acid obtain- The acid pre- 

 ed by the medium of charcoal, or that of sugar, afforded ferent^avs" 

 similar results. acted the saiu» 



SCIENTIFIC 



