BEN 



256 



BEN 



tMte of soda thus formed is decomposed by sulphuric acid, 

 which, combining with the soda, separates the bcnzoic arid, 

 the greater part of which is precipitated, owing to its alight 

 solubility. 



Benioic arid may also be precipitated by muriatic acid 

 from the evaporated urine of the cow, and some other ani- 

 mals, and also from the water which runs from dunghills. 

 The arid has a disagreeable smell, which may be neai 

 rl nf by boiling it in water with animal charcoal. When fat 

 and tallow are distilled an empyreumatic product is obtained, 

 which if boiled with powdered chalk in water, yields ben- 

 loate of lime, and this, upon the addition of muriatic arid, 

 gives bensoic acid ; it results from the decomposition of the 

 animal matter, was formerly supposed to be a peculiar 

 aci'l. and from its origin was called tebacic acid, 



The properties of bcnzoic acid are, that when pure it is 

 colourless ; it crystallizes in soft and rather elastic crystals, 

 which have scarcely any smell ; its taste is rather aromatic 

 and penetrating than sour ; by exposure to the air it under- 

 goes no change ; it requires two hundred times its weight of 

 cold or twenty-four of boiling water for solution ; on cooling, 

 a crystallized mass is obtained, which resembles fat in ap- 

 pearance ; alcohol takes it up readily and in large quantity ; 

 prismatic crystals are procured by the spontaneous evapo- 

 ration of the'spirit. The aqueous solution acts but feebly 

 upon litmus paper ; it combines readily with alkalis, earthy 

 and metallic oxides, forming salts which are called ben- 

 MM 



Benzoic acid fuses and sublimes at a gentle heat, but a 

 part of it is decomposed by the process : if strongly heated 

 it takes fire and burns with a bright yellow flame ; when 

 mixed with sand and heated, it yields more combustible 

 gase* than any other substance ; it dissolves in sulphuric 

 and nitric acid without being decomposed, 



Benzoic acid is a compound of hydrogen, oxygen and car- 

 bon ; but according to the experiments of Wb'hler and 

 Liebig, (An. de Chimie et de Physique, li. 273> it is to be 

 considered as the oxide of a compound inflammable body, 

 which they term benzule; this is composed of 5 equivalents 

 of hydrogen=5, 2 of oxygen=16, and 14 of carbon = 84, its 

 equivalent is consequently 105; anhydrous benzole acid 

 consists of 1 equivalent of benzule 105 + 1 equivalent 

 of oxygen = 8, its equivalent being 113; but the crystal- 

 lized benzoic acid contains in addition 1 equivalent of water, 

 making its equivalent 122 : this water cannot be separated 

 by heat, and it exists in the benzoate of lead, but not in tlml 

 of silver, whMi is anhydrous. 



The saline compounds of benzoic acid are not very impor- 

 tant; the alkaline and earthy salts are generally soluble in 

 water, and so also are some of the metallic benzoates, 

 especially 'hose of manganese, nickel, and cobalt, whid' the 

 perbenzoate of iron is insoluble ; advantage has been taken 

 of this property to separate peroxide of iron from the oxides 

 above named. For this purpose it is requisite that the iron 

 should be entirely in the state of peroxide; the solution 

 should contain no excess of acid, and the benzoate Khould 

 be perfectly neutral ; when these precautions are duly ob- 

 served, a pale red insoluble perbenzoate of iron is j.recipi- 

 tated, which is stated to be separable by hot water into a 

 soluble su penal t and an insoluble subsali. 



The benzoates of lead, mercury-, and silver are among the 

 more insoluble salts of this acid; when the benzoate of 

 ammonia is added to a solution of nitrate of silver, a white 

 pulverulent anhydrous benzoate of silver is precipitated ; it 

 is, however, completely soluble in boiling water, and is 

 deposited M the solution cools in brilliant foliated crystals. 



BENZOIC ACID is obtained from several sources, such 

 as from benzoin by sublimation, or by precipitation, for 

 lime and the fixed alkalies extract it from benzoin, and 

 from these it can be separated by the addition of an acid, 

 t in lo obtained from balsams, of which it is an essential 

 constituent ; from certain fragrant substances, such as va- 

 nilla, canella bark, ambergris ; from some grasses, and the 

 Ivacous. It exists in the form of a benzoate in 

 the unne of infants, in that of many herbivorous animals, of 

 the beaver (cat for flbrr), and even of the dog. 



There is some difference in the qualities of the acid, txc- 

 <\K to the source whence it in obtained : for medical 

 purposes the acid procured from benzoin by sublimation, 

 and termed flower* of benzoin,' should alone be used. 



Sublimed brnz<>ir acid occur* in white, needle-like prisms, 

 which, when in mass, have a flocculent appearance, with a 

 oft, silky lustre. The odour is said to be owing to a little 



empyreumatic oil ; the taste is at first sweetish, but oftcr- 

 . cry pungent ; the specific gravity is 0'G5". Its acid 

 quality is manifested by reddening turmeric paper ; it is 

 scarcely soluble in water, whether warm or cold ; it is com- 

 pletely soluble in alcohol: it therefore enters into the com- 

 position of the Tinrtura camphor-' .<! O f the London 

 Pharmacopoeia, and the Tinctura opii ammoniulij of the 

 Kdinburgn Pharmacopoeia, two preparations loty; known 

 under the name of paregoric elixir. The use of these re- 

 quires care and judgment. [See BALSAMS.] 



Benzoic acid has been recommended to lie inhaled \\ith 

 the \apouruf water in consumption and spasmodic .i-umi.i. 

 In the former of these diseases it is of no ellieacy, and in 

 the latter of very little. Benzoic acid, combined with ex- 

 tract of conicum, forms a useful expectorant in the humid 

 asthma of old or feeble persons. 



BENZOIN or BENJAMIN, a resinous substance com- 

 monly but improperly termed a gum. It is extracted from 

 the Styrax benzoin, which grows in Sumatra, by making 

 incisions in the trunk. It hardens very quickly, and is 

 imported in the state of brittle masses, which when fractured 

 present n mixture of white, brown and red grains, fre- 

 quently as large as an almond. The fracture of benzoin 

 is conchoidal, and the lustre is greasy ; its specific gra\ity 

 is from 1063 to 1*092. Its smell is agreeable, resembling 

 that of vanilla. It melts at a moderate heat, and \ 

 bet'zoic acid, of which it contains about eighteen per cent. 



.According to the analysis of Unverdorben, benzoin con- 

 tains besides benzoic acid and a little volatile oil, three 

 different resins. If benzoin be reduced to fine powder, and 

 boiled in an excess of a solution of carbonate of potash, the 

 benzo'c acid, and a resin are dissolved, which may l.e 

 precipitated together by muriatic acid ; when the precipitate 

 is boiled in water, the acid and a little extractive matt, 

 dissolved, and the resin is left, amounting to about 03 of 

 that of the benzoin ; this resin is of a deep brown colour : it 

 is soluble in concentrated alcohol, but slightly so in ajther 

 and volatile oils, and insoluble in the oil of petroleum. 

 Ttas resin is weakly electro-negative ; it does not decom*K>se 

 acetate of copper, but precipitates acetate of lead ; carbonate 

 of potash dissolves it but slowly. The compound of this risin 

 with potash is soluble in anhydrous alcohol but neither in 

 nether nor in oil of turpentine. The aqueous solution is preci- 

 pitated by muriate of ammonia. The greater part of benzoin 

 is insoluble in solution of carbonate of potash, and it '. 

 a bright brown residue ; from this nether extracts one resin 

 and leaves another. When the aether is evaporated, the resin 

 dissolved in it remains. It is very soluble in alcohol and in 

 oil of caraway, but not in oil of petroleum. It does not de- 

 compose acetate of copper: it dissolves readily in potash, 

 and is not precipitated from solution by excess of it. Am- 

 monia does not dissolve it; its compounds with earthy and 

 metallic oxides are insoluble in tether. 



The resin, which is insoluble in carbonate of potash, and 

 remains unacted upon by aether, is brownish. It is soluble 

 in alcohol, but not in the volatile oils nor ammonia. Potash 

 dissolves it readily, but a great excess of the alkali precipi- 

 tates the compound which is formed. This and the iornn-r 

 resin, when precipitated by an acid from solution in potash 

 and exposed to the air while moist, are converted into the 

 first resin, or that which is dissolved by carbonate of potash 

 and alcohol. If the two last resins be subjected to dry dis- 

 tillation, they yield at first a volatile oil, which is \ei-v 

 slightly empyreumatic, and which, like the oil of bitter 

 almonds, is converted by the action of the air into benzoic 

 acid. 



Benzoin is employed in the preparation of benzoic acid ; 

 it is also used by perfumers. 



BENZOIN is improperly called a gum, since it is quite 

 insoluble in water, and appears to be intermediate between 

 resins and balsams. It is a natural production of several 

 plants, but is yielded only by one in sufiicic-nt quantity to lie- 

 worth collecting. The Styrax benzoin of Dryander, or 

 Lithocarpus benzoin, as it is called by Blumc, was ascer- 

 tained by the former of these naturalists to be the source of 

 this substance, and was described and figured by him in the 

 Phit'>s. Trans, of 17S7, vol. Ixxvii. p. 307, t. 12. Previous 

 to his time it was supposed to be obtained from the IMUI-US 

 lintznin, though Linntcus had pointed out the incorrectness 

 of this opinion, and from the Terminaliaangufli/olia(Jaf<\.), 

 which possess the odour, but yield little of tlie substance. 

 Tin- odour i also imparted by some grasses, such as the 

 Anthoxanthum odoratum (sweet-scented vernal meadow 



