ALB 



•dditlon of hfat ; imj duriiig the proccfs, there Joes not 

 ■ppc;ir to l>c any iiicrcafe or diminiition of weight. In hir- 

 tlicr coiiilniiuuoii of this mcilioj of aecour.tliig foi ti.e fad, 

 tht following ingcniiuis cxpcrinunts were invented by tlic 

 Swcdilh clicfliill. Having mix.ed one part of white of 

 cg^ with four parts of water, lie divided the iniifs into two 

 equal parts, and added to one a folution of Lauilic alkali, 

 and to the other the fame quantity of tarhoiiated alkali ; 

 the luiuor, in boiii cafes, remained perfectly clear ; then, 

 upon dropping into tlie firll a little mmiaiic acid, an im- 

 mediate coagulation took place, while a like quantity of 

 acid produced no efTeit on the latter folution. 'I'his is ac- 

 counted for hy bcheele in tlit following manner. By the 

 combination of acid with caullic alkali, the heat given out 

 li abforbed l.y the albumen \\lueh thus coagulates, but when 

 the acid is added to the carbonated alkali, tl\e whole of tiie 

 caloric is taken up by the dilcngagcd carbonic acid, and in 

 confcquence no coagidalion ii the refult. 



According to Tourcroy, the coagulation of albumen is 

 owing to an abfoqitiou of oxygen, and the facts wljich 

 appear to Fiim to prove this are the following : If the red 

 oxyd of mercuiy is triturated with albumen, it is reduced 

 to the ftate of black oxyd, at the fam.e time that the albu- 

 men becomes opake, thick, and in fome degree coagulated. 

 The white of a frelh laid egg is incapable of being reduced 

 by boiling to fo firm a conliitence as that of an egg w Inch 

 lias been kept feveral days. 



On the other hand, Can-adori has (licwn that albumen is 

 coagulablc by heat without the accefs of air, and even that 

 when this efl'cA takes place in oxygen gas, there is not the 

 fnialleil portion of air abforbed. 



It was the opinion of Bucquet, that albumen is a kind of 

 natural foap, and that its coagulation by acids was merely 

 owing to their combination with the foda which it contains. 



Thefc differences between chemills of acknowledged abi- 

 lity, founded alfo upon undifputed fafts, appear to arife 

 from a iniAaken neceflity of confidering coagulation as the 

 conttant effeft of fome one uniform caufc, when a little 

 confideration cannot fail of convincing us of the very equi- 

 vocal nature of this phenomenon. Albumen certainly con- 

 cretes by the mere aftion of heat unafliHed by any other 

 fubftance j and this is probablv owing in part to the fixation 

 of caloric, and in part to the difengagement of fulphurated 

 hydrogen, as is manifell from the tarnilliing of filver, and 

 the +ilackening of acetatcd lead, by the white of a newly- 

 boiled egg ; that the extrication of fulphurated hydrogen 

 is a nccefiary concomitant in moil catcs of the coagulation 

 of albumen, is obvious alfo from certain other facts ; thus 

 coagulated albumen is foluble in a very dilute acid, and 

 upon the addition of a few drops of a more concentrated 

 one, is immediately precipitated, at the fame time that a 

 Itrong fmell of fulpliurated hydrogen is m.anifefted. Again, 

 nitrated filver inttantly coagiriates albumen, and black 

 ftreaks at the fame time begin to appear, owing to the for- 

 mation of hydrofulphuret of filver. The coagulation pro- 

 duced by the red oxyd of mercury may be occafioned by 

 the abforption of oxygen, if indeed the blacknefs of the 

 mercury is not rather produced by combination with fulphu- 

 rated hydrogen ; and this is the more probable, as even 

 metallic mercury undergoes a iyi^.ilar change. The thicken- 

 ing produced by mctaUic falts, is neither caufcd by the 

 mere communication of heat nor of oxygen, fince the coagu- 

 lum is an imputrtfcible combination of the albumen with 

 the metallic oxyd. In like manner a coagulation is formed 

 by the combination of albumen with tan'KIN. which has 

 alfo a fpecific chemical action. Laftly, pure alcohol will 

 coagulate albumen, probably by the mere abllraftion of 

 the wate» nccefiary to its liquidity, fince the curd thus 



ALB 



obtained is rcfoKibk in water, without any ivmarkable 

 change of properties. 



Betides the general effect of acids on albumen, fome 

 of them produce peculiar changes which require notice. 

 Bv concentrated iiilphuric acid it is blackened and charred, 

 exhaling at the fame time a naufeous odour ; while, by the 

 fame acid diluted, it is merely coagulated and prefcrved 

 from further change. Strong muriatic acid gives a violet 

 tinge to the coagukim, and by long coutaft cffeCls a par- 

 tial decomjjolition, fo far as to become faturated with am- 

 monia. Nitrous acid, at the temperature of about 70° 

 Fahr., caufes a plentiful difengagement of azotic gas ; if 

 further heated, a quantity of pruffic acid is formed ; and 

 this change is immediately rendered fenfible, by the pe- 

 culiar odour of this acid, (imilar to that of bitter almonds ; 

 this is fuccceded by the feparation of carbonic acid and 

 carbonated hydrogen ; and as foon as this change comes 

 on, the refidue in the retort is found to confifl of httle 

 elfe than water, covered with a lemon-coloured fat oil, 

 and holding in folution oxaUc acid, which may be after, 

 wards feparatod by cryllallization. If dry cauftic patafh 

 or foda be triturated with albumen, either liquid or 

 folid, ammoniacal gas is fet at hbeity ; and the calcination 

 of the refidue yields a pruiliatcd alkali, capable of pro- 

 ducing a blue precipitate with the falts of iron. 



The neutral falts appear to have little or no aftlon, ex*. 

 cept that of preferving the albumen from putrefaftion. 



By fpontaneous decompofition in the open air, albumen 

 palTes rapidly, and probably without firll becoming acidi 

 into the putrid fermentation ; in this ftate it exhales a fetid 

 odour, aifumes a brown colour, gives out ammonia, and 

 remains a confiderable time before the decompofition is 

 completed. 



Animal albumen, as contained in milk, blood, and eggs> 

 formiS a confiderable part of the food of man. Advantage 

 is taken of its property, of coagulating by heat, to clarify 

 liquors of various kinds : it is largely ufed in the arts of 

 leather dreffing and fugar refining, and the more tranfparent 

 kinds are employed for varnifhes. Didl. Mettiod. Art. Al- 

 bumine. Fourcroy Syil. des Connaif. Chimiq. vol. ix. 

 Scheele's Eflays. Annales de Chimie, vol, xxix. 



Albumen, Vegetable, The difcovery of albumen 

 in vegetables is due to Fourcroy. This chemift having ob- 

 ferved that the clarification of the expreffed juices of the 

 antifcorbutic plants was effected by the fpontaneous coagu- 

 lation of their colouring matter, at the temperature of boil- 

 ing water, was induced to examine whether this property did 

 not depend on the prefence of albumen. For this pur- 

 pole, having obtained the juice of two pounds of young 

 crefles, he hltcred it while cold, through blotting paper, 

 and by this means feparated the grolTer parts of the co- 

 louring fccuia : the liquor was, however, ftill of a bright 

 green, but upon being expofed in a broad {hallow veffel to 

 the air, at a temperature of about 80° Fahr,, in two hours 

 it became turbid and depofited a greenifh matter, becoming 

 itfelf almoft colourlefs ; in this ftate it was expofed to the 

 hxat of boiling water, and in a few minutes there feparated 

 a large quantity of whitilh ilocculent matter. Another por- 

 tion of the fame clarified liquor being expofed to the air, 

 depofited at the end of two days a fimilar coagulum ; 

 and the fame efieft was produced on a third portion by the 

 addition of fulph-uiic acid. The fubftance thus obtained 

 being nrft repeattdly wafhed in cold water, exhibited all 

 the properties of animal albumen. It was eafily and 

 quickly difToIved hy any of the alkalies ; it experieMiced 

 no change in boihng water, except that of becoming more 

 fohd ; it converted the purple juice of mallows to green, ■ 

 and by diftillation, yielded a notable quantity of ammonia : 



when 



