S'^-l Experiments and Remarks on a Substance 



found^p resemble precisely the tannin of galls and of other 

 naturaf substances*. 



C. Carbonate of potash, when added to a solution of the 

 artificial tanning substance, deepens the colour ; after which 

 the sokuion becomes turbid and deposits a brown magma. 



D. Five grains of the dry substance were dissolved in 

 half an ounce of strong ammonia ; the whole was then eva- 

 porated to dryness, and, being dissolved in water, was found 

 not to precipitate gelatine, unless a small portion of muriatic 

 acid was previously added. 



E. Another portion of the same substance, which had 

 been dissolved in ammonia, was evaporated in along-necked 

 matrass, and was kept in very hot sand during half an hour ; 

 at first some ammonia arose, and afterwards a yellow liquor 

 which had the odour of burned horn. The residuum was 

 then examined, and was found to be nearly insoluble in 

 water, to which it only communicated a slight yellow 

 tinge. 



F. It is remarkable that the dry artificial tanning sub- 

 stance, although prepared from vegetable matter, should, 

 when placed on a hot iron, emit an odour very analogous 

 to burned animal substances, such as born, feathers, &c.; 

 this I found also to be the case in the experiment which has 

 been related, and I was desirous, therefore, to ascertain more 

 accurately the effects of heat on this substance when di- 

 stilled in close vessels. 



I took some very pure vegetable charcoal which had been 

 exposed to a red heat in a retort for more than an hour, 

 and by nitric acid converted it into the artificial tanning 

 substance. 



']\ventv grains of this, rendered as dry as possible, were 

 put into a small glass retort, to which a proper apparatus, 

 terminating in a jiir filled wilh quicksilver, and inverted in 

 a mercurial trough, was adapted. The retort was placed in 

 a small furnace, and was gradually heated by a charcoal fire 

 until the bulb became red hot. 



When the retort became warm, and after the expulsion 

 of the atmospheric air, a very small portion of water arose, 

 which settled like dew on the sides of the vessels : this 

 was succeeded bv a little nitric acid, from which the tan- 

 ning substance had not been completely freed; and soon 

 after a yellowish liquor came over, which was in so very 

 small a quantity as only to slain the upper part of the neck 



* Mr. Davy on the Constituent Parts of Abtilngcnt Vcgx't;;b]cs. Phil. 

 •iV.ir.s. ISO.'J." I). 'jn, LMl. 



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