452 Notices respecting New Books. 
tion of acetate of lead, or by a piece of silver; and lastly, that 
this sulphuretted hydrogen seems owing to the spontaneous dis- 
colourment of the tincture itself. 
The Professor proceeds to examine the changes of colour in the 
tinctures of orchella, violet, Brazil and Campeachy woods, &c. 
The orchella owes its name toa native of Florence, its reputed 
discoverer about the beginning of the 14th century, called Orri- 
cellaria or Rucellai; but, like most of the Florentine arts, is most 
probably of Greek origin. Both the aqueous and spiritous tine- 
tures of orchella manifested the same changes and characters as 
the tincture of turnsole. The orchella of commerce is of two 
kinds; one called *‘ vegetable or Canary orchella,” which is pre- 
pared by fermenting the Lichen rocella with urine, and the other 
“earthy orchella,” prepared fromthe Lichen Parillus of Auvergne. 
The aqueous tincture changes colour more rapidly than the spi- 
ritous ; but the other results are similar, and prove that the eo- 
louring principle of turnsole and orchella is the same as alleged 
by Chaptal, who learned the fact from an English tract om eo- 
lours, by Wilson, published about half a century ago, a work al- 
most unknown in England at present, but which has been deeply 
studied by Chaptal and other French chemists, and in which 
will be found the germ of many of their professed modern disco- 
veries. The tincture or infusion of violets, sometimes called sy- 
rup, because the latter was formerly used in medicine, changed 
from blue to purple or violet, at the same time it evolved carbonic 
acid gas, and regained its colour by the addition of a very small 
quantity of a solution of common potash or tin. The infusion of 
violets may therefore be kept in a tin vessel several years, and be 
still fit for chemical purposes. The colouring matter in the roots 
of Anchusa tinctoria L. is soluble in alcohol and in oil, but not 
in water. A strong spiritous tincture kept seven months in an air- 
tight bottle without undergoing any alteration. Similar and even 
still more extensive experiments were performed on the colouring 
matter of Brazil or Pernambuco wood (Cesalpinia echinata), 
Brasiletto (C@esalpinia Sapan) or wood of St. Martha, Cam- 
peachy wood (Hematoxylon Campechianum), and on nephritic 
wood, the Moringa Zeylanica. ‘The aqueous infusion of the 
last is celebrated by Newton for having the property of refracting 
the yellow or orange rays of light and reflecting the blue, of be- 
coming yellow even with reflected light by means of an acid, and 
of re-assuming the blue by the addition of an alkali. The au- 
thor has found that several varieties of ebony, sandal, and iron 
wood have the same properties, and his observations on guaiacum 
confirm those of Mr. Brande, It appears that a little Brazil- 
wood sawdust mixed with some natron or impure carbonate of 
soda, aud put into a tumbler of water, immediately communi- 
cates to it the colour and appearance of red wine; and that bi 
this 
