Process for depriving Vinegar, &c. of their Colour. 1 29 



from the paper and pencil by the naked eye. The two re- 

 flections are effected in the interior of a four-sided glass 

 priMii, at two posterior surfaces inclined to each other at 

 an angle of 135 degrees. In the construction formerly 

 described, the two other surfaces of the prism are both 

 plane, through which the rays are simply transmitted at 

 their entrance and exit. But since an eye that is adjusted 

 for seenig the paper and pencil, which are at a short di- 

 stance, cannot see more distant objects distinctly without 

 the use of a concave glass, it may be assisted in that re- 

 spt-ct by a due degree of concavity given to either, or to 

 both the transmitting surfaces of the prism. It is, how- 

 ever, to the upper surface alone that this concavity is 

 given ; for, since the eye is then situated on the side toward 

 the centre oF curvature, it receives all the benefit that is 

 proposed from the periscopic principles. 



XX. M. V\G\j\v.-R.'s new Processfor depriving Vinegar and 

 other Vegetable Liquids of their Colour*. 



J. HE agent employed is animal charcoal, and the process 

 is easy, oeconomical, and may be applied with equal facility 

 in the large as in the small way. To take away the colour 

 of vinegar, a litre of the red kind (red wine vinegar) cold, 

 i.s mixed with -15 grammes of bone charcoal, in a glass 

 yesse! : this mixture is shaken from time to time, and in 

 two or three days the colour disappears so completely that 

 when filtered through paper it passes perfectly limpid, 

 without having lost any of its taste, smell, or acidity. 

 When the i)rocess is to be performed in the large way, the 

 charcoal is thrown into a cask of vinegar, which must be 

 stirred from time to time to renew the points of contact. 

 In the large way not above half the proportion of charcoal 

 is required as for small quantities : the colour does not 

 vanish so instantaneously, but the result is certain, nor 

 does the length of lime the vinegar is left in contact with 

 ihe charcoal at all injure it. 



Vineiiar thus rendered limpid may be rendered aromatic 

 by infuiing plants in it before discoloration, or by mixing 

 with it afterwards a small quantity of alcohol charged with 

 the aromatic principle. It is then preferable to any other 

 vinegar for the table, the toilet, pharmacy, and pickling 

 green fruits. 



The liighest coloured red wines treated in the same 



• Abriilgcd from Ann. tU Chim. 



Vol.41. No. 178. /"e^. 1813. I manner 



