CHEMISTRY. 



121 



Chemical mixed with its own weight of charcoal powder, wood- 

 Esamina. as hea, quicklime, or porcelain clay, and sublimed, it was 



Nature bta i ned in a state of P ur 'ty. 



-_V J^ Its smell, when pure, resembles that of common cam- 

 phor, but is not so strong. Its taste also resembles that 

 of camphor. It swims on water, to which it commu- 

 nicates its taste, and burns upon its surface. It dissolves 

 completely in alcohol, and is precipitated by water. Ni- 

 tric acid, of the specific gravity 1.261, had no action on 

 it, though it readily dissolves common camphor ; but 

 concentrated nitric acid dissolves it with the disengage- 

 ment of nitrous gas ; and water does not precipitate it 

 from its solution as it does common camphor. Acetic 

 acid does not dissolve it. When heated it sublimes 

 without decomposition ; and when set on fire it burns 

 like camphor. 



SECT. XXII. Of Bird lime. 



Bird-lime. The vegetable principle to which we give the name of 

 bird-lime, was first examined by Vauquclin, who found 

 it possessed of properties different from every other. It 

 was found collected on the epidermis of a plant brought 

 to Europe by Michaud, and called robinia ritcosa by 

 Cels ; constituting a viscid substance, which made the 

 fingers adhere to the young twigs. From the late ana- 

 lysis of bird-lime by Bouillon la Grange, it is obvious 

 that it owes its peculiar properties to the presence of an 

 analogous substance, which indeed constitutes the essen- 

 tial part of that composition. Hence the reason why 

 we have given the name of bird-lime to the principle it- 

 self. 



Natural bird-lime (or that which exudes spontaneously 

 from plants), possesses the following properties: 



Its colour is green ; it has no sensible taste or smell ; 

 is extremely adhesive ; softens by the heat of the fingers, 

 and sticks to them with great obstinacy. When heated 

 it melts, swells up, and burns with a considerable flame, 

 leaving a bulky charcoal behind it. It does not dissolve 

 in water ; alcohol has but little action on it, especially 

 when cold. By the assistance of heat it dissolves a por- 

 tion of it ; but on cooling, allows the greatest part to 

 precipitate again. When exposed to the air it continues 

 glutinous, never becoming hard and brittle like the re- 

 sins. 



It combines readily with oils. Ether is its true sol- 

 vent, dissolving it readily without the assistance of heat. 

 The solution is of a deep gretn colour. The alkalies do 

 not combine with it ; the effect of the acids was not 

 tried. These properties are sufficient to distinguish 

 bird-lime from every other vegetable principle. 



Artificial bird lime is prepared from different sub- 

 stances in different countries. The berries of the misle- 

 toe are said to have been formerly employed. They were 

 pounded, boiled in water, and the hot water poured off. 

 At present bird-lime is usually prepared from the middle 

 bark of the holly. The process followed in England, as 

 described by Geoffroy, is as follows : The bark is boiled 

 in water seven or eight hours, till it becomes soft. It is 

 then laid in quantities in the earth, covered with stones, 

 and left to ferment or rot for a fortnight or three weeks. 

 By this fermentation it changes to a mucilaginous con- 

 sistency. It is then taken from the pits, pounded in 

 mortars to a paste, and well washed with river water. 

 Bouillon la Grange informs us, that at Nogent le Ro- 

 trou bird-lime is made by cutting the middle bark of the 

 holly into small pieces, fermenting them in a cool place 

 for a fortnight, and then boiling them in water, which is 



TOL. VI. PART I. 



afterwards evaporated. At Commcrci various other 

 plants are used. 



Its colour is greenish, its flavour sour, and its consist- 

 ence gluey, stringy, and tenacious. Its smell is similar 

 to that of linsoed oil. When spread on a glass plate, and 

 exposed to the air and light, it dries, becomes brown, 

 loses its viscidity, and may be reduced to powder ; but 

 when water is added to it, the glutinous property returns. 

 It reddens vegetable blues. 



When gently heated it melts, and emits an odour like 

 that of animal oils. When heated on red hoat coals, it 

 burns with a lively flame, and gives out a great deal of 

 smoke, leaving a white ash, composed or carbonet of 

 lime, alumina, iron, sulphate, and muriate of potash. 



Water has little action on bird-lime. When boiled 

 in water the bird-lime becomes more liquid, but recovers 

 its original properties when the water cools. The water, 

 by this treatment, acquires the property of reddening 

 vegetable blues, and when evaporated leaves a mucilagi- 

 nous substance, which may be likewise separated by al- 

 cohol. 



A concentrated solution of potash forms with bird- 

 lime a whitish magma, which becomes brown by evapo- 

 ration, while ammonia separates. The compound thus 

 formed is less viscid than bird-lime, and in smell and 

 taste resembles soap. In alcohol and water it dissolves 

 almost completely, and possesses properties similar to 

 those of soap. 



Weak acids soften bird-lime, and partly dissolve it ; 

 strong acids act with more violence. Sulphuric acid 

 renders it black ; and when lime is added to the solution, 

 acetic acid and ammonia separate. Nitric acid cold has 

 little effect ; but when assisted by heat it dissolves the 

 bird-lime ; and the solution, when evaporated, leaves be- 

 hind it a hard brittle mass. By treating this mass with 

 nitric acid, a new solution may be obtained, which by 

 evaporation yields malic and oxalic acids, and a yellow 

 matter which possesses several of the properties of wax. 

 Cold muriatic acid does not act on bird-lime ; hot muri- 

 atic acid renders it black. 



Alcohol of the specific gravity 0.817 dissolves bird- 

 lime at a boiling heat. On cooling, it lets fall a yellow 

 matter similar to wax. The filtered liquid is bitter, 

 nauseous, and acid. Water precipitates a substance simi- 

 lar to resin. 



Sulphuric ether dissolves bird-lime readily, and in 

 great abundance. The solution is greenish. When 

 mixed with water, an oily substance separates, which has 

 some resemblance to linseed oil. When evaporated, a 

 greasy substance is obtained, having a yellow colour and 

 the softness of wax. Oil of turpentine dissolves bird- 

 lime readily. 



Chemical 

 Examina- 

 tion of 

 Nature. 



SECT. XXIII. Of Rains. 



It is at present the opinion of chemists, that resins R es j M , 

 stand in the same relation to the volatile oils that max 

 does to thejired. Wax is considered as a fixed oil satu- 

 rated with oxygen ; resins, as volatile oils saturated with 

 the same principle. 



Resins often exude spontaneously from trees; they of- 

 ten flow from artificial wounds, and not uncommonly are 

 combined at first with volatile oil, from which they are 

 separated by distillation. The reader can be at no lost 

 to form a notion of what is meant by resin, when he is 

 informed that common rosin furnishes a very perfect ex- 

 ample of a resin, and that it is from this substance thai? 

 9 



