176 Observations on the Sulphurous Acid. 



pers, some syrup of violets diluted in water, in the propor- 

 tions mentioned above, and reddened by the same acids, I 

 poured drop by drop into each flask, Hquid sulphurous acid, 

 in a sufficient quantity to restore the blue colour; but before 

 adume a second drop of this acid, I took care to shake the 

 mixture strongly, and to observe the change in its colour : 

 this operation was performed upon, the nine flasks succes- 

 sively ; and the latter beino; corked, 1 allowed the whole to 

 rest for six liours. I observed, that during this time the 

 blue colour had become weaker, without any shade of red 

 having altered it. 



It was now necessary to examine if all the acids cm- 

 ployed in the preceding experiments had also the faculty of 

 reddening the syrup of violets rendered blue by the sulphu- 

 rous acid. The following is the result of my experiments : 



Fifth Experiment . — With the nitric, muriatic, sulphuric, 

 and phosphoric acids, the blue liquor became a wine red. 

 With the acetous acid it became a clear violet colour. 

 With the oxalic acid, a pale red. 



With the tarlarous, citric, and acetous acids, mixed in a 

 very large dose, no shade of red, nor any weakening of the 

 blue colour. 



Sixth Experiment. — Sidplairous acid gas and syrup of 

 violets diluted in ivuter, ar,d coumrcd red by different acids. — 

 We know that the sulphurous acid in the state of gas has 

 much more energy than in the liquid state. 



I was anxious to verify this fact, by an experiment upon 

 syrup of violets coloured red by the acids above mentioned. 

 For this purpose, 1 arranged the apparatus as if to prepare 

 the sulphurous acid. As soon as the second flask, filled two 

 thirds with distilled water, was saturated, I established a 

 communication between it and a third flask filled with a 

 mixture of water and syrup of violets, or reddened by sul- 

 phuric acid; a few bubbles of acid gas were suflicicnt for 

 giving the liquor its blue colour. 1 replaced this flask by 

 another, equally filled with syrup of violets diluted with 

 water, but reddened by another acid, and so on successively 

 imtil the whole mixtures reddened by the acids mentioned 

 in the first experiuient had been submitted to the action of 



the 



