CHEMISTRY. 



117 



tiun of 

 Nature. 



Chemical ways taken by chemists in the same acceptation. Par- 

 Examma- ment j cr has lately published a dissertation on the extracts 

 of vegetables, taken in the loose and general sense of the 

 word, which contains much information. 



The extractive principle possesses the following pro- 

 perties : 



Soluble in water, and the solution is always coloured. 

 When the water is slowly evaporated, the extractive 

 matter is obtained in a solid state and transparent ; but 

 when the evaporation is rapid the matter is opake. 



The taste of extractive is always strong ; but it is very 

 different according to the plant from which it is obtained. 



Soluble in alcohol, but insoluble in ether. 



By repeated solutions and evaporations, the extractive 

 matter acquires a deeper colour, and becomes insoluble 

 in water. This change is considered as the consequence 

 of the absorption of the oxygen of the atmosphere, for 

 which the extractive principle has a strong affinity. But 

 if the solution be left to itself, exposed to the atmo- 

 sphere, the extract is totally destroyed in const- quence of 

 a kind of putrefaction which speedily commence s. 



When oxymuriatic acid is poured into a solution con- 

 taining extractive, a very copious dark yellow precipitate 

 is thrown down, and the liquid retains but a light lemon 

 colour. These flakes are the oxygenized extractive. It 

 is now insoluble in water; but hot alcohol still dissolves 

 it. 



The extractive principle unites with alumina, and 

 forms with it an insoluble compound. Accordingly, if 

 sulphate, or muriate if alumina, be mixed with a solu- 

 tion of extractive, a flaky insoluble precipitate appears, 

 at least when the liquid is boiled ; but if an excess of 

 acid be present, the precipitate does not always appear. 



It is precipitated from water by concentrated sulphu- 

 ric acid, muriatic acid, and probably by several other 

 acids. When the experiment is made with sulphuric acid, 

 the fumes of vinegar generally become sensible. 



Alkalies readily unite with extractive, and form com- 

 pounds which are insoluble in water. 



The greater number of metallic oxides form insoluble 

 compounds with extractive. Hence, many of them, 

 when thrown into its solution, are capable of separating 

 it from water. Hence also, the metallic salts mostly 

 precipitate extractive. Muriate of tin possesses this 

 property in an eminent degree. It throws down a brown 

 powder perfectly insoluble, composed of the oxide of 

 tin and vegetable matter. 



If wool, cotton, or thread.be impregnated with alum, 

 and then plunged into a solution of extractive, they are 

 dyed of a fawn colour, and the liquid loses much of its 

 extractive matter. This colour is permanent. The 

 same effect is produced, if muriate of tin be employed 

 instead of alum. This effect is still more complete, if 

 the cloth be soaked in oxymuriatic acid, and then dipt 

 into the infusion of extractive. Hence we see that the 

 extractive matter requires no other mordant, than oxy- 

 gen to fix it on cloth. 



When distilled, extractive yields an acid liquid im- 

 pregnated with ammonia. 



It cannot be doubted, that there are many different 

 species of extractive matter ; though the difficulty of 

 obtaining each separately has prevented chemists from 

 ascertaining its nature with precision. Extracts are 

 usually obtained by treating the vegetable substance 

 from which they are to be procured with water, and 

 then evaporating the watery solution slowly to dryness. 

 All extracts obtained by this method have an acid taste, 

 and redden the infusion of litmus. They all yield a pre- 

 cipitate while liquid, if they are mixed with ammonia. 



Chemica? 

 Examina- 

 tion of 

 Nature. 



This precipitate is a compound of lime and insoluble ex- 

 tractive. Lime always causes them to exhale the odour 

 of ammonia. It has been ascertained, that the extrac- 

 tive principle is more abundant in plants that have grown 

 to maturity than in young plants. 



SECT. XVIII. Of the Narcotic Principle, 



It has been long known that the milky juices which Narcotic 

 exude from certain plants, as the poppy, lettuce, &c. principle, 

 and the infusions of others, as of the leaves of the digita- 

 lis purpurea, have the property of exciting sleep, or, 

 if taken in large enough dozes, of inducing a state re- 

 sembling apoplexy, and terminating in death. How far 

 these plants owe these properties to certain common 

 principles which they possess is not known ; though it 

 is exceedingly probable that they do. But as a peculiar 

 substance has been detected in opium, the most noted of 

 the narcotic preparations, which possesses narcotic pro- 

 perties in perfection, we are warranted, till further ex- 

 periments elucidate the subject, to consider it as the 

 narcntic principle, or at least as one species of the sub- 

 stances belonging to this genus. 



Opium is obtained from the papavcr album, or white How ob- 

 poppy, a plant which is cultivated in great abundance taiued. 

 in India and the East. The poppies are planted in a 

 fertile soil and well watered. After the flowering is over, 

 and the set-d capsules have attained nearly their full size, 

 a longitudinal incision is made in them about sun-set, 

 for three or four evenings in succession. From these in- 

 cisions there flows a milky juice, which soon concretes, 

 and is scraped off the plant and wrought into cakes. In 

 this state it is brought to Europe. 



Opium, thus prepared, is a tough brown substance, Its proper- 

 has a peculiar smell, and a nauseous bitter acrid taste. '"" 

 It is a very compound substance, containing sulphate of 

 lime, sulphate of potash, an oil, a resinous body, an 

 extractive matter, gluten, mucilage, &.C. besides the pe- 

 culiar narcotic principle, to which, probably, it owes its 

 virtues as a narcotic. 



When water is digested upon opium, a considerable 

 portion of it is dissolved, the water taking up several of 

 its constituents. When this solution is evaporated to 

 the consistence of a syrup, a gritty precipitate begins 

 to appear, which is considerably increased by diluting 

 the liquid with water. It consists chiefly of three in- 

 gredients ; namely, resin, oxygeni/ed extractive, and the 

 peculiar narcotic principle, which is crystallized. When 

 alcohol is digested on this precipitate, the resin and nar- 

 cotic substance are taken up, while the oxygenized extrac- 

 tive remains behind. The narcotic principle falls down 

 in crystals as the solution cools, still however coloured 

 with resin. But it may be obtained tolerably pure by re- 

 peated solutions and crystallizations. 



Water is incapable of dissolving the whole of opium. 

 What remain a behind still contains a considerable por- 

 tion of narcotic principle. When alcohol is digested on 

 this residuum, it acquires a deep red colour ; and depo- 

 sites, on cooling, crystals of narcotic principle, colour- 

 ed by resin, which may be purified by repeated crystalli- 

 zations. The narcotic principle obtained by either of 

 these methods possesses the following properties. 



Its colour is white. It crystalli/.es in rectanguLr prisms 

 with rhomboidal bases. It has neither taste nor smell. 



It is insoluble in cold water, soluble in about 400 parts 

 of boiling water, but precipitates again as the solution 

 cools. The solution in boiling water does not affect ve- 

 getable blues. 



It is soluble in 24 parts of boiling alcohol and 100 



