from gum thus (see p. 398) and is left behind in the still after the turpentine has come over; the melted rosin is run from the stills into moulds or barrels to cool. Rosin comes into the market in the form of large pieces, generally homogeneous, varying in colour and transparency; the best quality is known as "window glass" rosin, and is a pale amber in colour, perfectly clear and transparent; common" rosin is much darker in colour but is still homogeneous, clear and transparent; "black" rosin is very dark, almost approaching a black, and opaque. These varieties are dependent upon the quality of the original resin from which the rosin has been made; the so-called "virgin" resin gives the best rosin, while the resin collected later on in the season gives common rosin, and the scrapings of the resin from the bark, &c., give black rosin. Rosin is slightly heavier than water, its specific gravity being 1044 to 1.100; it easily melts; at about 177° F. it softens, ånd at 212° F. it is quite fluid; "windowglass" rosin forms a clear, limpid, yellow liquid. It is insoluble in water; is soluble in about eight times its weight of alcohol; in benzol, amyl alcohol, coal-tar naphtha, and acetone in almost any proportion; soluble in turpentine, ether, and most oils. It is also soluble in boiling solutions of the alkaline carbonates or hydroxides, becoming hydrolised and taking up the elements of water to form abietic acid, with which the alkalies combine to form the rosin soaps so largely employed in the soap industry. Rosin is a mixture of two acids bodies, pinic and sylvic acids, which are isomeric and have the formula C20 H30 O2. authorities consider that the composition of rosin is not that of a true acid, but an anhydride, abietic anhydride, which will take up water to form abietic acid.

Some

When distilled rosin yields a small quantity of acid water, spirit (see p. 409), a heavy oil (see p. 393), and a residue of pitch. It is used in making common oil varnishes, in making some cheap spirit varnishes, and in naphtha varnishes. By itself it leaves rather a hard, brittle, and lustrous coat, but tempered with some oil or soft resin it makes a durable varnish, not, of course, approaching the copals or kauri in this quality.

A solution in hot alcohol deposits crystals of sylvic acid on cooling. Nitric acid converts rosin into terebic acid, H C, H, 04 which is soluble in water.

Asphaltum.-Asphaltum or native bitumen is used in the varnish manufacture in the production of black varnishes, blacks, japans, &c. It was originally obtained from the shores of the Dead Sea, and this variety is specially designated Bitumen of Judea and Egyptian asphaltum, but it is imported from other

places, Altona in Albania, Coxitambo in South America, and Barbados, while there is an almost inexhaustible supply in the great lake of Trinidad. Asphaltum, when pure, is a blackishbrown solid, breaking with a conchoidal fracture, the surfaces being bright and lustrous. At 100° C. (212° F.) it melts to a black liquid having a strong pitchy odour. It burns with a bright somewhat smoky flame. In water and alcohol it is insoluble. It dissolves readily in coal-tar naphtha, but not so readily in turpentine. Its specific gravity varies from 1.00 to 1.20.

When used alone, simply dissolved in naphtha or turpentine, it dries with a gloss, with, however, a very brittle coat that in time begins to crack very much; on this account asphaltum, formerly much used by artists, has of late years been abandoned for oil painting.

In making japans and black varnishes its brittleness has to be overcome by the use of oil and other gums. Asphaltum is generally considered to be a product of the decomposition of animal and vegetable organic matter.

Artificial Asphaltums are now made by mixing together in various proportions coal-tar pitch, wool pitch, rosin pitch, and other pitches obtained in the distillation of animal and vegetable oily products. These are very useful in making cheap black varnishes, but considerable care must be taken in their selection, as many of the pitches, especially those from petroleum and paraffin, will not dry.

ETHEREAL-VARNISH RESINS.-This is an important group of resins, which are more or less soluble in such solvents as benzol, coal-tar naphtha, turpentine, ether, acetone, &c., and which are used with these solvents to make varnishes for special purposes. This group includes :

All oil varnish resins after they have been fused.

Dammars.

Mastic.

Sandarac.

Rosin.
Manila copal.

Some of these have already been described.

Dammar.— Under the name of Dammar there is imported into this country, for making varnishes, several kinds of resins, principally from Siam, which do not differ very much from one another in their properties.

1. Singapore dammar, also known as white dammar, is the true dammar. It is the produce of the Amboyna pine, Dammara orientalis, a large tree indigenous to Malacca, Java, Sumatra, Borneo, and the Malaccas, growing in the hill districts; in Java

it is cultivated to a small extent. The supply principally comes from Java through Singapore. The resin exudes from certain excrescences which grow a short distance above the root of the tree; in Sumatra and other places the resin exudes out in large quantities, while in other localities the natives make incisions in the excrescences to promote the flow of the resin; large quantities of the resin are also found in the river courses, having probably fallen from trees growing on the sides of the rivers. The resin exudes also from the upper portions of the trees, branches, &c.; the resin from the roots is usually in the form of large rounded knotty pieces, while that from the branches is more or less stalactitic in form.

Singapore dammar comes into commerce in the form of nodules, varying in size from an inch to 1 inches, sometimes larger, covered with a powdery crust; the interior is usually clear and transparent and is nearly white in colour, at the most it has a faint straw tint. It is friable and breaks easily with a powdery fracture. It is not quite so hard as copal, but is harder than rosin; when fresh it has a faint agreeable balsamic odour, which disappears on keeping. Its specific gravity is 1.062 to 1.123. It is soluble in turpentine, ether, petroleum spirit, chloroform, and in oil, but only partially so in alcohol and amyl alcohol. That from Batavia dissolves more freely than the Singapore variety. The melting point of both is about the same, 260° to 300° F. It is used in making varnishes for coach and cabinet makers, for paper, for pictures, and it is used dissolved in benzol for mounting microscopic objects. Dammar gives a pale, hard varnish with a fair amount of lustre. It has the defect of being rather friable, so that if, when dry, the coat is rubbed with the fingers it becomes powdery.

2. Rock Dammar.-This resin, which is almost indistinguishable from the last variety, is the produce of two species of Hopeaviz., Hopea odorata, which grows in Burmah, about Rangoon, Pegu, Martaban, and Tenasserim; and Hopea micrantha, a native of the Malay States of Malacca, Sumatra, Borneo, and Labuan. There are great differences between the resins yielded by these two trees; that from odorata generally occurs in rounded pieces about the size of walnuts, and is pale in colour; colourless pieces are often found. The micrantha resin is rather darker and a little harder. Rock dammar is soluble in turpentine, and other solvents, and is of equal value with the Singapore and Batavian dammars.

3. Sal Dammar.-This is the produce of the Sal tree, Shorea robusta, which grows on the southern flanks of the Himalaya mountains along nearly their whole extent; it is also found among the hills of West Bengal, in Borneo, Sumatra, and in the

Malaccas; so that its range is a wide one. It occurs in long pieces of a stalactitic character, rather brittle, mostly of a pale cream colour, more or less opaque and striated as if the pieces were formed by the separate flow of different streams of liquid resin, each of which solidified before the succeeding one had begun to run. Its specific gravity ranges from about 1097 to 1.123. It is soluble in ether, benzol, and turpentine, partially soluble in alcohol; the solutions are not quite clear, but always have a more or less turbid appearance.

It is not often met with in the English market. It is used in making paper varnishes and tracing paper, as, when dissolved in turpentine, it gives a good, pale, hard varnish which dries well and is elastic.

4. Black Dammar.-Black dammar, known in India as kala dammar, is the produce of several species of Canarium trees, principally Canarium strictum which grows in the Tinevelly district. The resin is collected in a very different manner from that adopted with other resins; the natives in the hot season make a number of vertical cuts just above the base of the trunk and then set fire to the tree below these cuts; by this means they kill the tree, which is now left for two years, at the end of which time a quantity of resin will have exuded from the trunk; this resin is collected in the months of February and March. resin flows for some years after the tree has been killed. In the Coimbatore district a somewhat different system is used to collect the resin; firewood is piled round the tree to the height of about 1 yard; this is fired and allowed to burn out; the resin subsequently exudes from the tree to about as high as the flames of the fire extended. The flow lasts for 10 to 12 years, and principally occurs during the months of November and April; generally, the resin is collected in January.

The

A tree will yield 200 lbs. of resin. Black dammar occurs in large black or brownish-black pieces, which are opaque when viewed in the mass, but in thin slices are transparent; it is homogeneous and vitreous in structure, breaking with a clear, conchoidal fracture. Specific gravity, 1.090. It is not very soluble in cold alcohol, but dissolves in hot alcohol; it is soluble in turpentine. On distillation it yields a large quantity of oil resembling rosin oil.

It is used in India for making varnishes, but in this country it is rarely seen, and it is doubtful whether there would be much demand for it, as, on account of its colour, it cannot be used for many kinds of varnishes and for some purposes it cannot compete with the cheaper rosin.

Mastic.. This resin is the product of the lentisc tree, Pistachia lentiscus, which grows in all countries washed by the Mediterranean; Spain, Portugal, Italy, Greece, the islands on the Greek, Turkish, and Levant coasts, North Africa, &c. The principal portion of the mastic comes from the district around Chios, one of the principal islands of the Greek archipelago. The mastic tree is shrubby, growing to a height of from 4 to 5 feet; the bark contains numerous resin vessels from which the resin is exuded in fairly large quantities on making excisions. About the months June to August the natives of the mastic district make many vertical incisions in the bark of the stem and branches, keeping these open during the period mentioned; the resin flows freely and soon becomes dry and hard; about two or three weeks after the cutting the resin is collected in small paper baskets, great care being taken to keep the resin clean; with the same object the ground below the tree is kept free from loose dirt, so that any resin which may accidentally fall from the tree may not get dirty. The lower branches of the tree frequently exude resin spontaneously; this is considered to be of a superior quality and is kept apart from the rest. A tree in good condition will yield from 8 to 10 lbs. per annum, but in the rainy season only lb., showing a considerable difference in the yield, which is much less in such seasons.

Mastic is sent into commerce in several forms :-1st, Cake, which is in the form of large pieces, and is the best quality of mastic; this variety is largely used as a chewing gum in Turkey. 2nd, Large mastic; this variety is mostly used as a chewing gum. 3rd, Small mastic; this occurs in small tears, and is the variety mostly met with in this country and which is used for making varnishes and for other industrial uses.

Mastic comes in the form of small tears of from to an inch long, mostly of a pale yellow colour, but sometimes they have a faint greenish tint; old specimens are darker than fresh samples. The outer surface of the tears is often powdery and the tears appear to be opaque; sometimes the tears are quite clear and transparent. Mastic is rather brittle and breaks with a conchoidal glassy fracture. Fresh mastic has a pleasant balsamic odour. It softens readily when placed in the mouth, a character distinguishing it from sandarac, which resembles it in form. Its specific gravity is about 1.056 to 1.060; it melts at from 105° to 120° C. (221° to 248° F.); but softens below 100° C. It is soluble in turpentine, alcohol, chloroform, amyl alcohol, and acetone, but not in petroleum spirit. It is used in making varnishes for pictures; a combination of mastic varnish and