These numbers give C16 Hg O, + BaO for the rational formula of orsellesiate of baryta. Orsellesic Ether. When (alpha) orsellic acid is boiled for some hours in strong alcohol an ether compound is formed. This ether is most advantageously prepared from the gelatinous precipitate obtained from the lime solution by muriatic acid. This precipitate, when it has been cautiously dried, is to be boiled for six or seven hours in strong alcohol. The solution is then to be cautiously evaporated on the water-bath till nearly the whole of the alcohol has been driven off; care, however, being taken not to evaporate it to dryness, otherwise much of the ether would be converted into a resinous matter. The residue is then to be boiled with a considerable quantity of water and filtered. On the cooling of the liquid the ether precipitates in long flat needles, which have at first a yellowish colour from adhering resin, but when they are treated with animal charcoal and recrystallized they are quite colourless. This ether cannot be distinguished in its external properties from the lecanoric and the erythric ethers. When it is distilled with dry potash it gives off alcoholic vapours, and orcin remains in the retort. Its reactions with aminonia and hypochloride of lime are similar to those of orsellesic acid. It might naturally have been expected that, as orsellic acid was the acid employed in its formation, this ether would have been the orsellic ether. From the results of the subjoined analysis I have been unable to deduce the formula which the orsellic ether ought theoretically to have, while the analyses agree pretty well with the formula of the orsellesic ether. I am therefore disposed to regard this compound as the orsellesic ether, the more so as I have ascertained that by merely boiling orsellic acid in water without the presence of a base, it is resolved into orsellesic acid. In a subsequent part of this paper, in the case of evernic acid, an instance of the formation of an ether of a second acid different from that of the acid originally put into the alcohol appears to occur. I. 0.327 grm. ether dried at 212° FAHR., gave 0·734 carbonic acid and 0·1842 water. II. 0.3195 grm. ether gave 0.716 carbonic acid and 0.177 water. The rational formula of orsellesic ether, therefore, appears to be C16 Hg O7+C, H2O. Roccella tinctoria from the Cape of Good Hope. This lichen, the history and botanical characters of which were partially described in a previous part of this paper, was pronounced by Dr. SCOULER to be also a large variety of the Roccella tinctoria. It contains two crystalline principles, one very similar to orsellic acid, and another with much less determinately acid characters, to which I have given the provisional name of roccellinin. These two principles may be both extracted by treating the lichen with milk of lime, and precipitating with muriatic acid in the way already described. The gelatinous mass which precipitates consists of a mixture of both principles; but they may be easily separated, as the roccellinin is quite insoluble both in cold and in hot water, while the acid analogous to orsellic acid, and which I purpose to call (beta) orsellic acid, is pretty readily soluble in boiling water. By repeatedly treating therefore the mixture of the two substances with boiling water and filtering, the (beta) orsellic acid is dissolved and deposited on the cooling of the liquid in small silky crystals. These crystals may be obtained quite white and of a much larger size by repeatedly crystallizing them out of weak spirits, care being taken not to boil the solutions. The (beta) orsellic acid may also be prepared by boiling the lichen repeatedly with water, in the way already described for (alpha) orsellic acid. The orsellic acid prepared by this process crystallizes in small silky needles, which are quite free from roccellinin, but which still retain traces of a fatty acid and a little resin, from which I could only purify them by dissolving them in lime or baryta water, precipitating by muriatic acid, and treating them in the way already described. (Beta) Orsellic Acid. The following are the characters of (beta) orsellic acid when purified by repeated crystallizations out of weak spirits. Its aqueous and alcoholic solutions redden litmus paper. It is soluble in hot and cold alcohol, and in ether. A solution of hypochlorite of lime yields the same fugitive blood-red colour with it as with (alpha) orsellic acid, with erythric acid, and with the colouring principle in Lecanora tartarea. The action of ammonia on all these bodies appears perfectly similar. (Beta) orsellic acid yields but a trifling precipitate with acetate, but a bulky white precipitate with subacetate of lead. In short, it is intermediate in its properties between (alpha) orsellic acid and erythric acid, but approaches the former more closely. I. 0·2535 grm. acid dried at 212° FAHR., gave with chromate of lead 0.558 carbonic acid and 0.1155 water. II. 0-2555 grm. substance gave 0.564 carbonic acid and 0·121 water. The rational formula of the hydrated (beta) orsellic acid is C34, H17, 014+HO. Baryta Salt. The baryta salt of (beta) orsellic acid is prepared in exactly the same way as the (alpha) orsellate of baryta, by dissolving the acid in an excess of baryta water in the cold, removing the excess of baryta by a stream of carbonic acid gas, collecting the precipitates on a filter and drying them. The organic salt was then separated from the carbonate of baryta by means of hot alcohol, out of which it crystallized in small white prismatic needles. Per cent. I. 0.237 grm. salt gave 0.067 BaOSo3=0.0439 BaO=18:52 BaO. with chromate of lead 0·6275 carbonic acid and 0·1285 HO. Calculated numbers. Found. The rational formula of the salt is C34 H17 O14+BaO. When (beta) orsellic acid is exactly neutralized with lime or baryta and boiled for a short time, it is decomposed just as (alpha) orsellic acid is when similarly treated, yielding a crystallizable acid, which I shall call (beta) orsellesic acid, whose properties very closely resemble those of (alpha) orsellesic acid. (Beta) orsellesic acid also forms a very soluble baryta salt, which crystallizes in long four-sided prisms. When an aqueous solution of (beta) orsellesic acid is boiled, it gives off carbonic acid and is wholly resolved into colourless orcin, exactly in the same way as (alpha) orsellesic acid. A more precise examination of this and another corresponding acid derived from erythric acid will form the subject of a future communication. An ether compound may be readily procured by boiling pure (beta) orsellic acid in strong alcohol, evaporating the solution, and treating the residue with boiling water in the way already described for orsellesic ether. It may also be prepared by boiling the crude precipitate already mentioned, consisting of orsellic acid and roccellinin, when dried, in strong spirits. In this case the ether is apt to contain a little roccellinin, but from this it can be easily separated by crystallizing it out of boiling water, in which the roccellinin is nearly insoluble. The ether compound crystallizes on the cooling of the liquid in long flat prisms, which cannot be distinguished in appearance from the orsellesic, lecanoric or erythric ethers, with which bodies in its properties and reactions it very closely corresponds. I. 0.365 grm. ether dried at 212° FAHR., gave with chromate of lead 0·814 carbonic acid and 0.206 water. II. 0.396 grm. ether gave 0·882 carbonic acid and 0.219 water. This substance when distilled with caustic potash gave off alcoholic vapours, leaving orcin in the retort. It is certainly an ether, but of what acid I am unable to determine. These analyses do not agree with the formula of (beta) orsellic ether. It is not improbable therefore that it is the ether of (beta) orsellesic acid, but this is a point which can only be determined when that acid has been subjected to analysis. Roccellinin. The Cape of Good Hope lichen contains a much larger quantity of roccellinin than of (beta) orsellic acid. The most convenient mode of extracting the roccellinin is by drying the gelatinous mass precipitated from the lime solution of the lichen by muriatic acid, and then boiling it for a considerable time in strong spirits. The orsellic acid is generally converted into the ether compound, while the roccellinin remains unchanged. On evaporating the solution nearly to dryness, and then treating the residue with boiling water, the ether compound is readily removed, while the roccellinin remains undissolved. By boiling the roccellinin in a large quantity of strong spirits it also dissolves, and on the cooling of the liquid it is deposited in long white hair-like crystals. By repeated crystallizations out of strong spirits, aided by a little animal charcoal, the roccellinin is rendered perfectly pure. It consists of soft hair-like crystals of a silky lustre, and about half an inch long, usually arranged in stars. If these crystals, when treated with hypochlorite of lime, acquire a reddish tinge, they are impure, from containing a little adhering orsellic acid. When quite pure, hypochlorite of lime gives them a greenish-yellow colour, which is permanent. Roccellinin requires a considerable quantity of boiling alcohol to dissolve it, and it is but very moderately soluble either in cold alcohol or in ether. It dissolves readily in the fixed alkalies and in ammonia. Its solutions remain quite colourless. When roccellinin is boiled in baryta water no carbonate of baryta is deposited, and a hot solution of caustic potash is equally inoperative upon it. When it is boiled in alcohol, saturated with muriatic acid gas, no ether is produced. I. 0.406 grm. substance dried at 212° FAHR., gave with chromate of lead 0.9328 CO2 and 0.1785 water. II. 0.351 grm. gave 0.807 carbonic acid and 0.156 water. The results of these analyses agree pretty closely with the formula C38 H17 O15, which however is merely empirical. I have made many attempts to determine the atomic weight of roccellinin by endeavouring to combine it with the alkalies and earths so as to form definite salts, but hitherto without success. It produces no precipitate with acetate or subacetate of lead, or with nitrate or ammonio-nitrate of silver. When a current of chlorine gas was passed for four days through a quantity of roccellinin diffused through water, the roccellinin assumed a slightly yellow colour. It was collected on a filter and washed to free it from adhering muriatic acid; when crystallized out of alcohol its properties were unchanged, and when subjected to analysis it contained no chlorine. Nitric acid in the cold had no action upon it, with the assistance of heat it converted it into oxalic acid. An attempt was made to prepare a baryta salt by boiling the roccellinin with freshly-precipitated carbonate of baryta. A quantity of prismatic crystals were obtained, but the quantity of base they contained varied according to the concentration of the solution. With caustic baryta, magnesia and lime, the results were equally unsatisfactory. When dissolved in an excess of ammonia and dried in vacuo, it was found to be unchanged, and to contain no ammonia. Roccellinin appears therefore to be a very indifferent body, which, like santonin, enters into no stable combinations with either alkalies or acids, though it appears to have a slight affinity for bases, and may therefore be regarded as a feeble acid. I am quite unable to determine what relation roccellinin bears to the orsellic series of acids, with which, however, it is not improbably connected, as the (beta) orsellic acid appears to be partially replaced by it in the Cape of Good Hope lichen. Roccella Montagnei. This lichen, which is imported in large quantity from the Portuguese settlement of Angola, and also from Madagascar, where it grows upon trees, was examined by Mr. SCHUNCK under the name of Roccella tinctoria var. fuciformis. Dr. ScOULER pronounces it to be the R. Montagnei of BETENGER, who found it growing on mango trees at Madras. The branches of the true R. fuciformis are much rounder than those of the R. Montagnei, which are nearly quite flat. This lichen is by much. the richest in colouring matter of any of those employed by the archil manufacturers. Mr. SCHUNCK extracted its colouring principle by treating the lichen with boiling water, and purifying the crystalline precipitate by repeatedly crystallizing it out of weak spirits. This is a very wasteful process; Mr. SCHUNCK states that he only got 60 grs. of erythric acid from a pound weight of lichen. The erythric acid employed in my experiments was prepared partly in this way, but chiefly by the more economical method of macerating the lichen in milk of lime, as already described. By the lime process, the average product of crude erythric acid amounted to twelve per cent. of the weight of the lichen employed. The erythric acid prepared by either method * See Voyage aux Ind. Orient. |