BRA

BRA

and it is on many accounts more convenient toarrange the fpathoie iron among the ores of-this metal, and to make diftin£t fpecies ofbraunfpath and calcareous fpar.

It occurs chiefly in veins accompanied by cal-careous fpar, fpathofe iron ore, galena, blende,^pyrites, yellow copper, and various ores of filver.It is found in the mines of Norway, Germany ,Sweden, France, Hungary , and England. AtOrmes head, in Caernarvonfhire, it is found inveins with copper and manganefe, and alfo veryabundantly in mafs.

BRAZIL WOOD or Fernamlottc TVood. SapanWood. The tree which bears this wood is theCaefalpina Crifta, Linn. The wood is very hard,takes a high polifli, and is fo heavy as to fink inwater. When chewed it gives a fweetifh talle.It much refembles in appearance Red Saunderswood, but differs from it eflentially in readilygiving out its colour to water, which Saunderswood does not.

Brazil wood is valuable for the beautifulorange and red colours, in various fhades, whichit furnifhes to the dyer, but the colour is natu-rally very fugitive, though it may be to a certaindegree fixed by various mordants.

When rafpings of brazil wood are boiled forfome time in water they give a fine red decoc-tion. The refidue appears black, but alkalieswill continue to extract a colour from it afterthe aftion of water is exhaufted. Spirit of wineand ammonia alfo extract a colour with greatfacility, which is fomewhat deeper than thewatery decoction.

When fulphuric acid is added very graduallyto a frefli watery decodtion of Brazil wood, aa fmall quantity of red precipitate falls down,and the clear liquor now becomes yellow. Nitricacid produces a fimilar change, but the liquoris more of an orange. Moft of the other acidsalfo agree with the former in producing a redprecipitate, and leaving the clear liquor of dif-ferent fhades of yellow or orange. The alkaliesadded to this liquor reftore the original redcolour, but with a cafl of crimfon or violet.

Brazil wood dccoftion, or infufion in water,is readily turned of a violet or purple blue byalkalies, and this change is produced by fo veryminute a quantity as to furnifh a chemical teftof the prefence of alkalies, of very great utility.According to Bergman, b in his valuable analyfesof mineral waters, io grains of cryftallized car-bonat of foda, which contains no more thanabout 2.15 grains of mere alkali, difl'olved in aSwedHh kanne (5.5 Englilh pints) of water, give

* Berthxjflvt. . >

a fenfible purple tinge to paper reddened byBrazil wood. There is however fome ambiguityin this teft, as the fame change is produced bya folution of lime or magnefia in carbonic acidand water, a very frequent occurrence in moftnatural waters. Evaporating the water for fometime will diftinguifh whether the change onBrazil wood is produced by an alkali or a car-bonated earth ; for, if by the former, the purplewill be more intenfe in the concentrated water,as it now holds a greater proportion of alkali;but if by a carbonated earth, the effedl will beloft, as the boiling expels the loofe carbonicacid, and precipitates the carbonated earthwhich it held in folution. c

The effects of the folutions of tin and alumon Brazil wood are the moft important to thedyer. Alum added to the watery decoftion ofthe wood gives a copious fine red precipitate,inclining to crimfon and fubfiding flowly. Thefupernatant liquor alfo retains the original redcolour of the deco&ion, but if enough of alkaliis added to decompofe the alum, its earth fallsdown and carries with it nearly all the remainingcolouring matter of the wood. In this way afine crimfon Lake , imitating the cochineal car-mine, may be prepared, which therefore confiftsof alumine, intimately combined with the colour-ing matter of the wood a little heightened.

Nitro-muriat of tin added to the decoclionfeparates the whole of the colouring matter,which falls down in great abundance in unionwith the oxyd of tin, and the liquor remainscolourlefs. Even when the original colour ofthe wood has been previoufly altered by acids,the tin folution firft reftores the natural colour,and then precipitates the colouring matter aswith the frefli decodtion.

The folutions of iron blacken the decoflionor infufion of Brazil wood, (hewing the prefenceof the gallic acid.

Many of the other metallic folutions a£t fimi-larly to that of tin, in forming lakes, confiftingof the colouring matter of the wood united withthe metallic oxyd of the folution employed.

The colour of Brazil wood, though highlybeautiful is readily fugitive, and has the ad-ditional diiadvantage of being darkened andrendered purple by foap, which therefore can-not be employed in wafhing cloth dyed withthis colour. Acids render the colour permanent,but change it yellow. It is peculiarly dit—tinguiihed from the colouring matter ol kermesand madder, by having the original crimfon-rcdreftored by folutions of tin, after having been

* Kir wan »n Min. Waters.