

CUE M ISTHV. 





white of evg, allowed IB run mto putrefaction, reiem. 

 blcs that of put. 



It i* insoluble in alcohol and ether, which immediate- 

 ly coaguUte it, uules> it be mixed with a very great pro- 

 portion of water ; in which case even acid* have DO ef- 



When acid* are poured upon it, coagulation takes 

 place equally ; but several of them have the property of 

 dissolving it again when assisted by heat. This at least 

 is the case with sulphuric acid. The solution is of a 

 green colour, and does not toon blacken even when boil- 

 ed. It is the case also with nitric acid, and probably 

 also with muriatic acid. Nitric acid first disengaged 

 some azotic gas ; then the albumen is gradually dissol- 

 ved, nitrous gas emitted, oxalic and malic acids formed, 

 and a thick oily matter makes its appearance on the sur. 

 face. 



None of the earths form insoluble compounds with 

 albumen ; in this respect they resemble the alkalies, 

 The case is different with the metallic oxides. 



Every metal tried, except cobalt, occasions a precipi- 

 tate ; but no precipitate ever appears when the oxide is 

 held in solution by an alkali or earth. The effect of the 

 metallic salts on albumen forms a striking contrast with 

 their effect on gelatine. 



From the experiments of Dr Bostock, it appears that 

 a drop of the saturated solution of oxymuriate of mer- 

 cury, let fall into water containing ^-^yth part of its 

 weight of albumen, produces an evident milkiness, and 

 a curdy precipitate falls. It is therefore a very delicate 

 test of the presence of albumen in animal fluids. 



If a solution of tannin be poured into an aqueous so. 

 lution of uncoagulated albumen, it forms with it a very 

 copious yellow precipitate of the consistence of pitch, 

 and insoluble in water. This precipitate is a combina- 

 tion of tannin and albuir.en. When dry it is brittle, like 

 over-tanned leather, and is not susceptible of putrefac- 

 tion. This property which albumen has of precipitating 

 with tannin was discovered by Seguin. 



The infusion of galls is by no means so delicate a test 

 of the pretence of albumen as of gelatine. When an in- 

 fusion of galls, containing - ', per cx-nt. of solid matter, 

 and water holding T '. . tli of albumen in solution, arc 

 mixed in equal quantities, no effect is produced at first, 

 but after some time a precipitating matter appears, and 

 slowly subsides. 



II. When albumen is coagulated either by heat, alco- 

 hol, or acii' :i opaque substance of a pearl white 

 colour, tough, and <;f a sweetish mucilaginous taste. It 

 it no longer soluble in water, and is not nearly so sus- 

 ceptible of decomposition as uncoagulated albumen. Mr 

 Hatchett kept it for a month under water, and yet it did 

 not become putrid. 



When this substance was digested for some hours in 

 water, it gradually softened, and became white and opake 

 like newly coagulated albumen. When water is made to 

 act upon it h.ng, a small portion of it is taken up. The 

 y liquid is not precipitated by the infusion of tan ; 

 but mtromuriate of tin occasions a faint cloud. 



According to Schecle, the mineral acids, when great - 

 ', diluted with water, dissolve a portion of coagulated 

 albumen, which is thrown down again by the same acids 

 concentrated. 



When coagulated albumen is steeped in diluted nitric 

 acid, the acid in about four 'weeks begins. to acquire a 

 yellow ting--, which becomes gradually deeper ; but the 

 albumen, though it becomes more opake, is not dissol. 

 w acid, wh n saturated with ammonia, 

 become* of deep crange colour, but does not let fall 

 uy precipitate. When the albumen, thus treated, ia 





immersed in ammonia, the liquid assumes a deep oran.;<- 



r, inclining to bin. il-ritl. The album. 

 dissolved, and the solution li.ts a deep yellov.-i.sh brov 

 lour. If tli^.' albumv 



lied a:id then boiled in w.r.tr, it i Ji> i 



forms a pr.lc yellow liquid, which L hm pro- 



perly concei.ti.ited. Ifth, again dis- 



solved in boil::r^ water, the solution is precipitated by 

 tan and by nitro muriate of tin. Hence we see that ni- 

 tric acid hai the propsrty of converting coagulated al- 

 bumen into gelatine. 



Concentrated nitric acid dissolves coagulated albumen 

 with effervesccr.ee, especially when assisted by heat. It 

 becomes orange bro\vn whpn mixed with amnv i.i.i, b. 

 no precipitate falls. 



It i; r, idily dissolved by boiling lixivium of potaslu 

 ammonia is disengaged, and an animal soap is formed, 

 soap, when dissolved in water, and mixed with acetic or 

 murintic acids, lets fall a precipitate winch is of a sapo- 

 naceous nature. When heated gently, some oil Aow 

 it, and a brownish viscid substance remains. The a 

 lies, when diluted, and not assisted by heat, act upon 

 it slowly and imperfectly. 



These properties indicate sufficiently that coagulated 

 albumen is a very different substance from uncoagulated 

 albumen. 



III. From the effects of nitric acid on albumen ; and 

 its products, when subjected to destructive distillation, 

 it has been concluded that it consists of carbon, hydro- 

 gen, azote, and oxygen. 



According to the experiments of Thenard and Gay- Co- 

 Lussac, its constituents are as follows : 



Carbon, 52.883 



Oxygen, 23.872 



Hydrogen, .... 7..'>l-<> 

 Azote, 15.705 



KM) 



Mr Hatchett has rendered it very probable that it is 

 the first of the soft part of animals that is formed, and 

 that all the other soft parts are formed from it. 



SECT. III. OfMitcut. 



No word in chemistry has been used with less preci- Muctu. 

 sion than mucus. Too many experimenters have made 

 it serve as a common name for every animal substance 

 which cannot be referred to any other class. Dr lios- 

 tock, in his excellent papers on the Analysis of Animal 

 Fluids, has endeavoured to fix the meaning of the word, 

 by ascertaining, the properties of pure mucus. Four- 

 croy and Vauquelin have lately written an elaborate pa- 

 per on the same subject. 



From Bostock's experiments it appears, that if the HOW ob- 

 solid matter obtained by evaporating saliva to dryness be tamed. 

 re-dissolvW in water and filtered, the solution will con- 

 tain very little except mucus. He obtained mucus, also, 

 by macerating an oyster in water, and evaporating the 

 liquid. Mucus, thus obtained, possesses the following 

 properties : 



1 . It has much the appearance of gum arable, except- j [t pri fti- 

 ing that, in general, it is rather more opaque ; like it, it tie*, 

 has little taste, dissolves readily in water, and forms an 

 adhesive solution. 



'_'. When evaporated to dryness, it is transparent, in- 

 eljbtic, and has much the appearance of gum. It is in- 

 tolublc in water, but dissolves readily in all the aciili, 

 though very much diluted. 



3. It does not dissolve in alcohol, nor in ether. 



k It docs not coagulate when heated ; nor when con- 



