114 



C H E M I S T R Y. 



Albumen- 



\V!n 11 this solution i* mixed with sufficient quantity 

 of lime, it form) a very good lute ; and bit* of linen dipt 

 in it adhere very strongly to other bodies. 



Ether doet not sensibly dissolve gluten. 



Acidi act upon gluten differently, according to the 

 peculiar properties of each. 



Concentrated acetic acid dissolves it readily in consi- 

 derable quantity, and without altering its nature. The 

 solution is muddy, but permanent ; and the gluten may 

 be thrown down by means of alkalies. This acid dis- 

 solves the fermented gluten of Cadet ; and the solution 

 may be substituted for the solution in alcohol as a var- 

 nish ; but it dues not answer to mix it with cut 



Concentrated sulphuric acid renders it violet culoured, 

 and at last black ; inflammable air escapes, and charcoal, 

 water, and a portion of ammonia, are formed. \Vln n 

 nitric acid is poured on it, and heat applied, there is a 

 quantity of az-'tic gas emitted ; and by continuing the 

 heat, some little oxalic acid is formed, and likewise ma- 

 lic acid, while a numb-r of y llow-coloured oily flakes 

 make their appearance in the solution. 



Muriatic acid dissolves gluten with facility when its 

 action i assisted by heat. When gluten is placed in 

 oxymuriatic acid, it softens, and seems to dissolve, but 

 soon coagulates again into yellow-coloured flakes, which 

 become transparent and greenish coloured by drying. 

 When heated, they exhale oxymuriatic acid, and assume 

 the appearance of common gluten. This acid has the 

 property of precipitating gluten from water in the state 

 of yellowish-white flakes. 



Alkalies dissolve gluten when they art assisted by 

 heat. The solution is never perfectly transparent. Acids 

 precipitate the gluten from alkalies, but it is destitute of 

 its elasticity. Alkalies, when much concentrated, form 

 with it a kind of soap, converting it into oil and ammo- 

 \vliich last is dissipated during the trituration. 



ma : 



Gluten is precipitated from water, and from some of 

 its other solutions, by the infusion of nutgalls. The co- 

 lour of the precipitate is usually yellowish-brown, and 

 it does not dissolve though the solution be heated. 



When moist gluten is suddenly dried, it swells ama- 

 zingly. Dry gluten, when exposed to heat, cracks, 

 swells, melts, blackens, exhales a fetid odour, and burns 

 precisely like feathers or horn. When distilled, there 

 come over water impregnated with ammonia and an em- 

 pyreumatic oil ; the charcoal which remains is with dif- 

 ficulty reduced to ashes. 



* 



SECT. III. Of Albumen. 



Albumen is the term by which chemists have agreed 

 to denote the while of egg, and all glary tasteless sub- 

 stances which, like it, have the property of coagulating 

 into a white, opaque, tough, solid substance, when heated 

 a little under the boiling point. This substance form', a 

 constituent of many of the fluids of animal bodies ; and 

 when coagulated, it constitutes also an important part 

 of their solid*. Substances analogous to it had been 

 noticed by chemists in the vegetable kingdom. Scheele 

 affirmed, as early as 1780, that the greater number of 

 plants contained a substance analogous tu curd. Four- 

 croy, about the year 1790, announced the existence of 

 albumen in a variety of plants ; hut Proust has since 

 hewn, that the substance which he took for albumen, 

 and which had been already examined by Rom-lie, was 

 not possessed of the properties which characterise that 

 animal matter. But Vauquclm has lately discovered al- 

 bumen in abundance in the juice ot the papaw tree ; so 



1 .11)11!, J. 



Mature. 



that its existence as a vegetable principle cannot be dis 

 pitted. 



The jtaiMic tree, the carica Jiapaya of botanist*, 

 grows in 1'tru, ice. and in the Isle ol France, win-re the 

 milky juice that exudes from it is baid to be employed 

 with efficacy againt the (iuiiicii icurni. Two specimens 

 of this juice were brought fiom that island to P^ris by 

 Charpentier de Cossigny. In the one, the juice had 

 bin t-vaporated to dry ness, and was in the state of an 

 extract ; in the other, die juice was preserved by being 

 mixed with an equal bulk oi rum. Both were subjected 

 to a che:nical analysis by Vauquelin. The first was of 

 a yellowish- white colour, and .-.emitranspart nt. Its taste 

 was sweetish. It had no smell, and was pretty solid ; 

 but attracted moisture when kept in a damp place. The 

 second was reddish brown, and had the smell and taste 

 of boiled beef. When the first specimen was macerated 

 in cold water, the greatest part of it dissolved. The 

 solution frothed with soap. The addition of nitric acid 

 coagulated it, and rendered it white ; and whe.i boned, 

 it threw down abundance of white flakes. These flakes 

 were coagulated albun.cn. 



Other specimens of this juice, both in the liquid and 

 dried state, have been examined more recently by Vauque- 

 lin, and likewise by Cadet. 



The essential characters of albumen arc the follow- 

 ing : 



In its natural state it is soluble in water, and forms a its pro- 

 glary limpid liquid, having very little taste ; which may pcrtiet. 

 be employed as a paste, and which forms a very shining 

 varnish. 



The solution is coagulated by acids, pretty much in 

 the same way as milk is coagulated by the same re-agents. 



When not too much diluted, it is coagulated also 

 when heated to the temperature of 176. 



Albumen dissolved in water is precipitated in the state 

 of brown flakes by the infusion of tan. 



The solution is equally coagulated when mixed with 

 alcohol. 



Albumen is precipitated from water in the state of 

 white powder by the salts of most of the white metals ; 

 such as silver, mercury, lead, tin, &c. 



The juice of the papaw possessed all these properties. 

 It therefore contained albumen. In few other vegetable 

 productions has this substance hi en yet found in such 

 abundance, or in a state in which its properties wen- so 

 decidedly characteristic! but the res> mblance betw.-en 

 the curd of milk and albumen is very close, as we shall 

 see afterwards. Now, Proust has ascertained that al- 

 mohds, and other similar kernels from which cmulsi,ns 

 are made, contain a substance which has the properties 

 of curd. 



Albumen, when burnt, emits ammonia ; and when 

 treated with nitric acid, yields azotic gas. It evidently, 

 then, contains azote. But as it is more properly an ani- 

 mal than a vegetable substance, we shall defer m 1 '- 1 '-, >' 

 farther account of its properties till we come to treat of 

 animal bodies. 



SECT. XIV. Of Fibrin. 



That peculiar substance which constitutes the fibrous 

 part of the muscles of animals, has been callrd.//'6r/n by 

 chemists. A substance resembling it, as it exints m the 

 blood, has been detected by Vauquelin in the juice of 

 the papaw tree ; the same juice which contained albumen 

 in such plenty. Fibrin, then, must be ranked among ve- 

 getable substances. 



3 



