610 CONIFERiE. 



Tirol/ observed that when a growing larch stem was sawn through, the 

 resin flowed most abundantly from the heart-wood, and in smaller 

 quantity, though somewhat more quickl}'', from the sap-wood, and that 

 the hark contained but few resin-ducts. The practice of closing the 



cavities is adopted, not only for the sake of preserving the wood 

 and for the greater convenience of removing the turpentine, but 

 also because it tends to maintain the transparency and purity of the 

 latter. 



Description — Venice turpentine is a thick, honey-like fluid, slightly 

 turbid, yet not granular and crystalline ; it has a pale-yellowish colour 

 aud exhibits a slight fluorescence. Its odour resembles that of common 

 turj)entine, but is less powerful ; its taste is bitter and aromatic. When 

 exposed to the air, it thickens but slowly to a clear varnish, and hardens 

 but very slowly when mixed with magnesia. Larch turpentine, though 

 • common on the Continent, is seldom imported into England,' and the 

 article sold for it is almost always spurious. 



Chemical Composition — Larch turpentine dissolves in spirit of 

 wine, forming a clear liquid which reddens litmus ; hot water agitated 

 with it also acquires a faint acid reaction, due to formic and probably 

 also to succinic acid. Glacial acetic acid, amylic alcohol, and acetone 

 mix with it perfectly. By distillation it yields on an average 15^per 

 cent, of essential oil of the composition, C^^ff^ which boils at 157' C, 

 and when saturated with dry hydrochloric acid gas, easily produces 

 crystals of the compound C^m^^ + HCL The residual resin is soluble 

 in two parts of warm alcohol of 75 per cent., and more copiously m 

 concentrated alcohol. 



Two parts of the turpentine diluted with one of benzol or acetone 

 deviate the ray of polarized light 9-5° to the right The essential oil 

 deviates 6'4° to the left; the resin perfectly freed from volatile oil and 

 dissolved in half its weight of acetone, deviates 12C)° to the right ma 

 column 50 mm. long. 



We have not Riippppdprl in r^ror^nvincr a. prv.^fn.llized acid from the 



turpentine 



American 



formed into crystallized abietic acid. 



Uses— Venice turpentine appears to possess no medicinal propeiw 

 that are not equally found in other substances of the same class, and a 

 a medicine it has fallen into disuse. But in name at least it is m »^' 

 quent requisition for horse and cattle medicines. 



Adulteration— Alston (1740-60) said of Venice turpentine' that i 

 is seldom found in the shops,~a remark equally true at the present aa^ 

 for but few druggists trouble themselves to procure it genuine. 

 Venice turpentine usually sold is an artificial mixture of conunon reb 

 and oil of turpentine, which may be easily distinguished from the P 

 duct of the larch by the facility with which it dries when spread on 

 piece of paper,*^ and by its stronger turpentine smolL 



■ffprfiu* 



^Boianische Zdtmg, xvii. (1859) 329, barrels imported from Trieste being o 

 abstracted m the JakresMu of Wiggers, 14 Jul,^ 1864-0. H ^^^. ^^ y,i 



3 Lectures on the Materia 



T^A^t!" ""^^ occasion I observed Venice Tiir- ii. (1770) 398. , ^ Venice 



pentme m a public drug sale in London, 21 * Thus if a thin layer of true \ enic 



tur 



