ON SULPHUROUS ACID. 



not admit, that the sphex foresees the egg it lays will pro- 

 duce a maggot, and will have need of all it provides for it : 

 according to him it does this merely for amusement, in imi- 

 tating what it perceived in its infancy. 



X. 



Observations on the Sulphurous Acid; by Mr. Planchk. 

 Read to the Society of Pharmacy, November the 15th, 

 1806*. 



1V1R. BERTHOLLET made known several remarkable Changes pro- 

 properties of sulphurous acid, in two excellent Memoirs, pS^^on 

 read to the Academy of Sciences in 1782 and 1789. In the sirup of violets 

 year 1796, Messrs. Fourcroy and Vauquelin read a much otheracfds'/ 

 more extensive memoir on the same subject at the Institute, 

 in which they gave a more complete history of this acid, 

 and of its different combinations. 



I have considered with great attention the labours of 

 these learned chemists, but among their numerous experi- 

 ments I do not find any, which actually relate to the object 

 of my present investigation ; the changes that liquid or ga- 

 seous sulphurous acid occasions in sirup of violets reddened 

 by different acids, and the contrary. This property of the 

 sulphurous acid I am more eager to make known, as it 

 may furnish matter for interesting reflections on the theory 

 of acids in general. 



The sulphurous acid I employed in my experiments was The acid pre- 



prepared by decomposing very pure sulphuric acid by means pare< ! ^.f 1 " , 

 c 11 • i phunc acid and 



ol mercury equally pure. In its preparation I followed mercury. 



the process of Berthollet. My sirup of violets was of a 



very fine blue, without any mixture. 



Experiment 1. Sirup of violets, diluted with eight parts Restored the 



of distilled water, and coloured red by nitric, muriatic, b,ue that had 

 iL-ii. ... been changed 



sulphuric, phosphoric, or acetic acid, resumed its blue red. 



colour on the addition of liquid sulphurous acid. The 



colour was not quite so intense indeed, as before it was 



changed red, but it had no mixture of the latter colour. 



4nnales de Chimie, Vol. LX. p. 254. December, 1806. 



Exp. 



