LOGWOOD.

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deep purple precipitate ; corrosive sublimate, an orange precipitate ; chlorideof antimony, a carmine precipitate ; nitrate of bismuth, a beautiful violetprecipitate.

When hsematin is treated with caustic ammonia it gives a violet liquid,which, when heated to ioo° in closed vessels for some time, becomes nearlycolourless, owing to the reducing adion of the ammonia. On cooling, thisliquid becomes almost solid, from the precipitation of a white flocculent sub-stance, soluble in acids, with a bright yellow colouration, and re-precipitablefrom that solution by alkalies, with a white colour. This substance, whichcontains the elements of hsematoxylin and ammonia, ads as an organic base,and it becomes rapidly blue in contad with air. Dr. Schiitzenberger ascer-tained that this body contains nitrogen combined in another form—an ammo-niacal salt.

When hsematoxylin is heated to 140°, with anhydrous acetic acid, it yieldsa bright brown acetic derivative, insoluble in water, but soluble in alcohol.On evaporating the alcoholic solution the material exhibits an amorphous,resinoid, very fusible substance. Prof. Erdmann gave the name of haemateinto the produd of the adion of hsematoxylin when it absorbs oxygen in thepresence of an alkali. When a saturated solution of hsematoxylin in ammoniais gently heated, and shaken about so as to promote contad of air, the liquidassumes a deep cherry-red colour and deposits granular crystals of haemateateof ammonia. When this is decomposed by acetic acid there is formed a bulkybrown-red precipitate, which, on drying, becomes deep green and exhibits ametallic hue. When reduced to a powder this body is red. Haematein issparingly soluble in cold water, but more readily at a boiling heat; it issoluble in alcohol, and slightly soluble in ether ; its composition is expressedby Ci 6H I2 06, differing from hsematoxylin only by two atoms less hydrogen.Its formation is shown by the following formulae :—

CtfiH^Oe + O^CrfHxaOfi+HaO.

Alkalies and ammonia dissolve haemateine, yielding solutions which are atfirst blue or purple, but become gradually brown on contact with air and ad-vancing oxidation. Hsemateate of ammonia is a deep violet powder, formedof very small microscopical four-sided prisms, which are transparent, solublein water, with a purplish colour, and in alcohol with a red-brown : thehasmateate of ammonia loses its ammonia at ioo°, or even in vacuo, oversulphuric acid. This salt precipitates solutions of metallic salts, giving riseto coloured precipitates,—as, for instance, with sulphate of copper, a violet-blue ; protochloride of tin, violet; iron alum, a black precipitate; nitrate ofsilver is reduced to the state of metal. Hsemateine is therefore only the firstterm of the process of oxidation of hsematoxylin. When the oxidation pro-ceeds farther ulmic compounds are formed, as is the case with the alkalinesolutions and under the influence of bichromate of potassa. Sulphurettedhydrogen decolourises haematein while combining with it, but does not re-convert it to hsematoxylin ; but probably the more energetic reducing adion°f bydriodic acid would effed the re-conversion.

The colourable substance of logwood ads as a phenol, capable of enteringinto combination with bases as well as with the radicals of the acids. In itsgeneral properties hsematoxylin very much resembles bresiline, but they are notidentical: it is probable, however, that haematin may be converted intobresiline by the addition of the phenyl radical.