BEN'ZOIC ACIP. 



KEXZOIC ALCOHOL. 



nitric acid convert* chlorobensoic acid into ttitrocUorobeiuoic acid 

 Chlorobenzoio acid combine* directly with single 



atom* of the metallic oxidm, forming therewith salts of which the 

 potaah and soda salts are uncrystollisable ; the ammonia salt is decom- 

 posed on evaporation. The baryta and lime salts are crystalliaable, and 

 both contain three atoms of water. The silver, lead, and copper salts 

 are insoluble, ami should therefore be prepared by double decom- 

 position : the first is crystalline, the two others amorphous. Chloro- 



banzoate of ethyl ( C "> Clt "{}o,J is a liquid which boils at 



473 Fahr. ; it is prepared by heating the free acid with alcohol and 

 sulphuric acid, and precipitation with water. 



An acid identical in composition with chlorobenzoic acid, when both 

 are in the free state, is prepared by distilling together salicylic acid 

 with pcntachloride of phosphorus, and boiling the oily distillate 

 (rectified at 392-480 Fahr.) with water. Hydrochloric acid is thereby 

 formed, and a crystalline substance separates out on cooling. This is the 

 new acid. It is purified in the same manner as described for chlorobenzoia 

 acid. The only observable difference between this body and chlorobenzoic 

 acid is in the melting point of the former, 266, and in the amount 

 of water contained in its salts ; the baryta salt being anhydrous, and 

 the lime salt containing only two atoms of water. This acid has con- 



equently been called paracMorobemoic acid. The bromine acid corre- 



(u 

 HOC,,,:'OA 



has been prepared by the action of bromine upon benzoic aoid iu the 

 sunlight, and by the gradual action of bromine vapour upon benzoate 

 of silver. Neither the free acid nor its salts have been much examined. 

 The free acid melts at 212 Fahr., and sublimes (but not without 

 decomposition). It is difficultly soluble in water, easily so in alcohol 

 and ether. 



Another substitution product of benzoic acid is the nitrob(n:oic acid 



(. IT \ 

 HOC,, ( v*J) KM- This acid, which contains an atom of peroxide of 



nitrogen, NO., in place of one of hydrogen, U a product of th. 

 of nitric acid upon benzoic acid. It is best prepared by mixing two 

 parts of nitrate of potash with one part of benzoic acid, and adding 

 enough strong sulphuric acid to form Hsulphate of potash ; the mass 

 being constantly stirred during the addition of the sulphuric acid. The 

 mass so obtained is heated until the nitrobenzoic acid melts ; it is then 

 poured off from the bisulphate of potash which has been formed, and 

 purified by recrystaUisation from boiling water. Nitrobenzoic acid 

 consists of colourless crystals, which sublime with partial decom- 

 position below their melting point, 338 Fahr., giving off suffocatim; 

 fumes. It is readily soluble in boiling water, difficultly so in cold 

 water. Nitrobenzoic acid decomposes the carbonates of the alkalies 

 and alkaline earths, forming monobasic salts of the general formula 



MO,C,,^' O | 0,. The potash, and toda taltt are difficultly crysfcdli- 



lisable ; the ammonia tail, as it exists in cold solutions, is decom- 

 posed by evaporation, an acid salt being funned. It is also gradually 

 converted, on digestion, into nitrobenzamide. The lime, ttrontia, and 

 baryta taltt are soluble and crystalline, and contain 2, 2J, and 4 atoms 

 of water respectively. The manganese tall is also soluble and crystal- 

 line, and contains four atoms of water, as also does the cadmium 

 palt, which is soluble but not crystalline. The setqui-mlt of iron 



I Fe,0,3C 14 f ^Q Jo,), and the :<'<, lilter, lead, and copper taltt, are 



insoluble, and are formed by appropriate double decomposition from 

 the ammonia salt. They are all anhydrous excepting the nitrobenzoate 

 of zinc, which contains five atoms of water. 



The nitrobenmatet of methyl and ethyl are prepared by dissolving 

 nitrobenzoic acid in the respective boiling alcohols, and satm.iti. >n 

 with gaseous hydrochloric acid. The hydrochloric acid should be 

 pawed through for a long time, and the product allowed to stand for 

 a day. On adding water, the corresponding nitrobenzoate is precipi- 

 tated. The nitrobenzoate of ethyl (c.H,OC 14 (" \0,} so obtained 



u agitated with a warm solution of carbonate of soda, and then washed 

 with cold water. The solid compound is then pressed between blot- 

 ting-paper, and recrystalliscd from a mixture of alcohol and ether. 



The nitrobenzoate of methyl f ^i^^nNO I ^V) '" ' 3tame d ' rom '** 

 alcoholic solution (and the same method may also be employed with 

 the ethyl compound) by evaporation. It separates out as fine needle- 

 shaped crystal*. The nitrobenzoate of ethyl melt* at 108* Fahr., and 

 boil* at 588'. The methyl compound melts at 158, and boils at 634. 

 Both nitrobenzoates are readily soluble in ether and alcohol, but in- 

 soluble in water. On boiling with hydrated potash, the alcohols are 

 regenerated, and benzoate of potaah formed. 



By the continued action of nitric acid, assisted by the presence of 

 sulphuric acid, upon benzoic acid, a second atom of hydrogen undergoes 

 replacement by another atom of peroxide of nitrogen, and an acid is 



formed having the composition HOC,. , J1.\ , 0, : this is binitroJ/emoic 



acid. To prepare it, small quantities of benzoic acid are successively 

 added to a mixture of fuming nitric and monohydrated sulphuric acids. 

 When complete solution ha* been effected, the product is heated for 

 several hour* until it begins to become turbid. It is then allowed to 

 cool, and is mixed with water. The insoluble flooculent portion is 

 washed with water, pressed between blotting-paper, and recrystaUiaed 

 in >m Killing alcohol, from which it crystallines in bright colourless scale*. 

 Binitrobenzoic acid is also soluble in ether, almost insoluble in cold, but 

 slightly soluble in boiling water. Strong nitric and sulphuric acids 

 dissolve binitrobenzoic acid iu considerable quantity without deoom- 

 . It is readily fusible, and may be sublimed with care without 

 decomposition. The salts of the alkalies with this acid, being soluble, 

 are prepared by direct neutralisation. The lead and silver compounds 

 are insoluble, and must therefore be formed by double decomposition. 



i*itrooen:oatc of ethyl ( C,H,0, C,,.jjy ^ 0,J is slowly formed upon 



boiling binitrobenzoic acid with alcohol. A portion of the binitro- 

 benzoate of ethyl separates from the alcoholic solution in oily drops ; 

 the remainder, which is dissolved in the alcohol, is precipitated theiv- 

 from, along with uncombined binitrobenzoic acid, on the addition of 

 water. The latter is removed by digestion with ammonia ; the pro- 

 duct thus purified is then washed with water and dissolved in boiling 

 alcohol. The pure ether separates from the alcoholic solution, on 

 cooling, in the form of long silky needles of a faint yellow colour. 

 Alcoholic ammonia converts binitrobenzoic acid into liiiii' 



|T % 



^ < " ii /vn \ n ) Caustic potash, when boiled with binitrobenzoate 

 ( --i H 3(* < O 4 ),O.,/ 



of ethyl, determines the formation of diuitrobenzoate of potaah and 

 the separation of alcohol. 



A port of the hydrogen of benzoic acid may undergo replacement by 

 chlorine, and another part by NO,, and the product still maintain iu 



acid character. Such is the tiltrochlorobcnzoic acid ( HOC,, Cl* 0,). To 



v NO, / 



prepare this acid, chlorobenzoic acid is treated with fuming nitrid acid. 

 The product, after standing some hours, is mixed with \\.it.i. \\hieh 

 after some days determines the separation of the new acid, in th- 

 of transparent tabular crystals, which melt at 244, and may be 

 illiscd from ether or alcohol, but not from water. The nt'fro- 

 clilorvbcnzoatct of baryta and tilrtr are both monobasic, and contain two 

 equivalents of water. The alter salt is crystalline, and tolerably .- 

 iu water ; the baryta one is amorphous, and more readily soluble. 



It is clear that anhydrous benzoic acid, (""H'O* I * na J' ^ ""w^ 

 as the oxide of an oxygen radical (C',,H,O,). This radical, which is 

 called beuznyl, may, like acetyl and the hydrocarbon radicals, play the 

 part of an atom of hydrogen. By the replacement of a portion of the 



hydrogen of ammonia by benzoyl, a substance, bemamide, N j jO"s> 



is obtained. [AMIDES.] 



BENZOIC ACID, Medical *tt of. There is some difference in the 

 qualities of the acid, according to the source whence it is obtained : 

 for medical purposes the acid procured from benzoin by sublim 

 and termed "flowers of lieiizoiii," should alone be used. 



Sublimed benzoic acid occurs in white, needle-like prisms, which, 

 when in mass, have a flocculent ..]].. -ar.in<-e, with a .-oft. silk\ 

 The odour is said to bo owing to a little cmpyreuuiatic "il : the taste 

 is at first sweetish, but afterwards very pungent ; the .--pivilie ; 

 is 0-657. Its acid quality is manifested by reddening ttm 

 it is scarcely soluble in water, whether warm ..i ...1.1; it is com. 

 soluble in alcohol : it therefore enters into the composition of the 

 Tinctura rnm/ihora; romfxfita of the ' London Pharmaco|xria.' and the- 

 Tiiictura ii/>ii ammontata of the ' Edinburgh Pharmacopoeia,' two pre- 

 ] orations long known under the name of paregoric elixir. The use of 

 these requires care and judgment. [BALSAMS.] 



Benzoic acid has been recommended to be inhaled with the 

 of water in consumption and spasmodic asthma. In the i . .1 

 these diseases it is of no efficacy, and in the latt. r .1 ran little. 

 Benzoic acid, combined with extract of conicnm. I..MH- . . 

 torant in the humid asthma of old or feeble persons. 



Benzoic acid alone, or in combination with ammonia, is of mi.! 

 value in the treatment of atonic gout. (See Urc in ' Medico i 'himrg. 

 Trans.' vol. xxiv. p. 30; and ' Pharmacciit. Trans.' vol. i. p. 24.) 



BENZOIC ALCOHOL. Hydrate o/ZWuyJ (c,.{}' j-O.J. ThisboJy, 



which stands to benzoic acid in the same relation as vinic alcohol to 

 acetic acid, is produced by the action of on alcoholic solution of potash 

 upon hydride of benzoyl : 



J(C 14 H,0, + KO, 110 = C 14 H,0, + C,,H,0,, KO. 



Hydride of bcnxorl. 



Bcnzoic alcohol. Bcnzoato of 

 Pouh. 



It is highly probable that the Tauri/lic Add found by Staedcler in the 

 urine of the horse and cow, and in human urine, is identical with 

 benzoic alcohol. Benzoic alcohol is a colourless oil, heavier than water. 

 It boil* at 400 Fahr. Oxidising agents convert it into benzoic acid. 

 just as they convert vinic alcohol into acetic acid. 



