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tine under the influence of oxygen and alkalis is so rapid that it may be used as a most délicate test of the présence of carbonate of lime in natural waters ; and it is a fact well-known to practical dyers, that waters con-taining a large quantity of carbonate of lime are well adapted for the production of good log-wood blacks. Hematine gives little or no colouration with salts of protoxide of iron, but hematëine gives a dark purplish blue ; the latter also gives dark blue précipitâtes, with salts of lead and tin. Hematëine is easily reduced to hematine by hydrogen and sulphuretted hydrogen.

In my opinion, the colouring matter in HematoXylum campechianum exists in the state of a glucoside, for when the trees are felled the wood is colourless ; but by the time the logs arrive here the outside is of a dark red colour, whilst the inside bas only become of a pale yellow colour.

As hematëine is the principle which the dyer requires, the logs are ground into a coarse powder, which is moistened and laid in beds 15 or 20 feet long by 10 or 12 broad, and about three feet thick. A slow fermentation ensues, by which the glucoside is decomposed and the hematine liberated. It is converted into hematëine by stirring the mass, thus exposing it to the oxygen of the air, the action being quickened by the ammonia of the atmosphère as well as by that given off by the décomposition of the azotised principles existing in the wood.

This prepared wood is used by the dyer to produce log-wood blacks, as I shall describe further on, and also by wood extract manufacturers, who préparé an extract which is muchusedincalico printing. To préparéthisextractitis necessary that the wood should not be too highly oxidised, and that the solution obtained from it by successive and repeated lixivation should be slowly concentrated at a comparatively low température, that is to say, not ex-ceeding 150° F. ; for if a high température be employed the hematëine is still further oxidised, and a dark purple resinous principle produced, which spoils the brilliancy of the colour.

This extract is chiefly used in print works, to produce purples in steam styles.* A strong log-wood solution is thickened with starch, and printed on a prepared cloth ; that is, a cloth that has been passed through a solution of stannate of soda, then through weak vitriol, by which means the binoxide of tin has been fixed as a mordant in the fibre of the cloth; thefabric,after washing and drying, is ready for the printer. After being printed, the cloth is either rolled on a perforated cylinder or hung in an iron chamber, and submitted to the action of steam, when the hematëine combines with the oxide of tin, producing a beautiful purple.

If blacks are to be produced, an iron mordant is fixed on the fabric, which is then passed through a logwood solution. It is afterwards washed, and the black fully developed by passing it through a hot dilute solution of bichromate of potash.

Log-wood and its extract are much used in Yorkshire for producing cheap blacks on mixed fabrics, which are goods in which the warp is cotton and the weft woollen. The black is produced by dyeing the fabric in a bath composed of logwood, sulphate of soda, and bichromate of potash.

It is often very useful to distinguish logwood blacks from sumach and other fast blacks, and logwood purples from aniline purples. This is easily effected by submit-ting the piece to the action of weak acids ; the logwood colours assume a bright red tint, while the others romain unchanged.

Brazil Wood.— We shall now pass on to a séries of woods which are all obtained from the genus Cesalpinia, belonging to the natural order Leguminosœ.

Although these woods have long been employed as

* Calico printers employ the word style or govels when speaking of a class of goods which are denoted by a word characterising the colouring matter used, or the method employed in producing them. Madder gcods and garancine styles may be given as examples of the first and steam styles of the second.

dyes by the natives of the countries where they grow, it is only since the introduction of Brazil wood by the Spaniards that their value as dye stuffs has been known in Europe. The best qualities are all imported from Brazil. The particular wood known as Brazil wood, derived from the Cesalpinia braziliensis, has become scarce in the market, from its having been all eut in the districts within easy distance of shipping ports.

The wood most in favour at the présent day cornes from Pernambuco, and is the Cesalpinia Christa. This tree is also found in Jamaica. That obtained from Sierra Nevada is not of such good quality.

Another variety, bearing the name of peach-wood, is chiefly derived from Nicaragua. A third, known as Sapan-wood, cornes principally from Siam, the East Indies, and other eastern countries. A rather inferior quality, known as Lima-wood, is imported from Peru.

All these woods appear to contain the same glucoside, and, like the previous ones, are decomposed by peculiar ferments, into a saccharine matter and a colour-giving principle. This is proved by the following experiments. if the décoction obtained by treating the wood from the interior of the sticks be boiled with a solution of double tartrate of potash and copper (the best known test for grape sugar), no precipitate is obtained; while if the glucoside be first decomposed by boiling with a dilute solution of hydrochloric or sulphuric acid, and afterwards treated with the copper sait, an abundant precipitate of suboxide is thrown down. The décoction, which bas only a faint yellow colour, gives a most abundant and brilliant precipitate with subacetate of lead. The colour-giving principle was discovered by M. Chevreul, who gave it the name of braziline. By oxidation it is converted into brazileine. It also combines with water, to form a hydrate containing two équivalents of water. Professor Bolley gives the formula of braziline as C2 2 H20 O7, and that of the hydrate C22 H2o O7 2 H2O. He has also made the curious observation that a comparison of the formulæ of hematine and braziline shows a différence equal to carbolic acid, as may be seen by the following table :—

Braziline C22H20, Hematine C16 H14 06

Différence Ce H. Ot Carbolic acid.

What is still more remarkable is, that by the action of nitric acid upon hematine, he obtained oxalic acid, whilst under similar circumstances braziline yields oxalic acid and picric or trinitrophenic acid, which is the product obtained when carbolic acid is acted upon by nitric acid.

A décoction of any of these woods becomes yellow or orange, (according to the quantity of braziline or brazi-lëine it contains) on the addition of an acid, and by the addition ofan alkali, a beautiful crimsonred, the shade of which varies according to the proportion of the two principles. It also becomes red with bichromate of potash, and gives a red precipitate with oxymuriate of tin.

These characters are sufficient to distinguish between a solution of these woods and one of log-wood.

To préparé a good commercial extract from these woods, they must be finely ground, as they yield their colour to water with difficulty ; like log-wood, they must be allowed to ferment and oxidise in the air, but not to the same extent. The concentration of the décoctions differs from that of logwood in the fact that they can bear a higher température. The more quickly they are evaporated the brighter are the colours which the extract gives. Dr. Dingler has proposed a process which is stated to givc very good results. It consista in adding 41bs. of gélatine, dissolved in water, to every cubic yard of ground-wood, and allowing the whole to ferment for severaldays. The wood so treated yields a stronger and richer extract than that obtained by the ordinary process ; no doubt the gélatine helps the décomposition of the glucoside, and the ammonia produced facilitâtes

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