PHARMACY. 



taining the elements of bad vinegar. As 

 a solvent, diluted alcohol perfectly super- 

 sedes the use of wine ; and if we wish to 

 use wine to cover the taste, or to assist 

 the operation of any medicine, M. Farm en- 

 tier proposes, that a tincture of the sub- 

 stance should be extemporaneously mixed 

 with wine as a vehicle. 



Notwithstanding this argument appears 

 to us to have great weight, we shall al- 

 low to the medicated wine;-, retained in. 

 the pharmacopoeias, the characters they 

 stiii generally possess. 



Vinum aloes, Lond. vinum aloes succo- 

 torinre, Edin. wine of aloes. 



Vinum gentians compositum, Edin. 

 \tine of gentian, compound. 



Vinum ipecacuanha;, Lond. Dubl. wine 

 >f ipecacuanha. 



Vinum nicotians tabaci, Edin. wine of 

 tobacco. 



Vinum rhabarbari, Lond. vinum rhei 

 palmati, Edin. wine of rhubarb. 



The metallic wines have been noticed 

 already. 



CLASS XIX. Extracta. EXTRACTS. 



Extract, in pharmacy, has been long 

 used, in the true and general sense of the 

 term, to express a substance extracted 

 from bodies of all kinds, by the action of 

 whatever menstruum, and reduced to 

 spissitude by the evaporation of that men- 

 struum. Of late, however, it has been 

 employed in a different and more limited 

 sense, as the name for a peculiar princi- 

 ple, which is often, indeed, contained in 

 extracts, and which before had no proper 

 appellation. It is in the former sense 

 that we employ it here, and in which we 

 wish it to be only used, while a new word 

 should be invented as the name of the 

 new substance. Till a better be propos- 

 ed we shall call it extractive. 



Extracts are of various kinds, according 

 to the nature of the substances from which 

 they are obtained, and the menstruum 

 employed ; but they commonly consist of 

 gum, sugar, extractive, tannin, gallic 

 acid, or resin, or several of them mixed 

 in various proportions. The menstrua 

 most commonly employed are water and 

 alcohol. The former is capable of ex- 

 tracting all the substances enumerated, 

 except the resin, and the latter all except 

 the gum. Wine is also sometimes em- 

 ployed, but very improperly ; for as a 

 solvent it can only act as a mixture of al- 

 cohol and water, and the principles which 

 it leaves behind on evaporation are rather 

 injurious than of advantage to the extract. 



Water is the menstruum most econo- 

 mically employed in making extracts, as 

 it is capable of dissolving all the active 

 principles except resin, and can have its 

 solvent powers assisted by a considerable 

 degree of heat. 



Watery extracts are prepared by boil- 

 ing the subject in water, and evaporating; 

 tlie strained decoction to a thick consist- 

 ence. 



It is indifferent, with regard to the me- 

 dicine, whether the subject be used fresh 

 or dry ; since nothing that can be pre- 

 served in this process will be lost by dry- 

 ing. With regard to the facility of ex- 

 traction, there is a very considerable 

 din* ere nee ; vegetables in general giving 

 out their virtues more readily \vl*en mo- 

 derately dried than when fresh. 



Very compact dry substances should be 

 reduced into exceedingly small parts, 

 previous to the allusion of the men- 

 struum. 



The quantity of water ought to be no 

 greater than is necessary for extracting 

 the virtues of the subject. This point, 

 however, is not very easily ascertained ; 

 for although some ot the common princi- 

 ples of extracts be soluble in a very small 

 proportion of water, there are others, 

 such as the tannin, of which water can 

 dissolve only a certain proportion, and 

 cannot be made to take up more by any 

 length of boiling, and we have no very 

 good method of knowing when we have 

 used a sufficient quantity of water ; for 

 vegetable substances will continue to co- 

 lour deeply successive portions of water 

 boiled with them, long after they arc 

 yielding nothing to it but colouring 1 mat- 

 ter. Perhaps one of the best methods is, 

 to boil the subject in successive quanti- 

 ties of water, as long as the decoction 

 forms a considerable precipitate with the 

 test which is proper for detecting the 

 substance we are extracting, such as a so- 

 lution of gelatine for tannin, of alum for 

 extractive, &c. 



" The decoctions are to be depurated 

 by colature ; and afterwards suffered to 

 stand for a day or two, when a conside- 

 rable quantity of sediment is usually 

 found at the bottom. If the liquor pour- 

 ed off clear be boiled down a little, and 

 afterwards suffered to cool again, it will 

 deposit a fresh sediment, from which it 

 may be decanted before you proceed to 

 finish the evaporation. The decoctions 

 of very resinous substances do not re- 

 quire this treatment, and are rather in- 

 jured by it; the resin subsiding along- 

 with the inactive dregs," 



