jfS On the Di/cokufatm of Silver l>y Bird's Eggs, i^fm. 



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On the Di/colouratien of Silver by Bird's Eggs, isfc. In a Letter from Anthoux Carlisle, 



E/q. 



To Mr. NICHOLSON. 



SIR, 



t , 



X PIAVE been lately occupied in tracing the natural hiftbry of bird's eggs, for a paper 



which has been in part laid before the Linnsean Society. Among other needful inquiries^ 

 I had occafion to make fome experiments on the properties of the Albumen, Vitellus, and; 

 Gas contained in the fdlliculus aeris of eggs, which belong more properly to chemical hif- 

 tory. As fome of the refults feem new, I beg leave to offer them for infertion in youv- 

 Journal-. 



The well known fa£t of filver beiiig difcoloured by eggs, induced me to try which of the 

 fubflances compofing a fowl's egg is the caufe of this appearance. I put the albumen, or. 

 white part of a new laid hen's egg, into a clean poliflied fiiver fpoon, and the intire vitellus,, 

 or yolk,, freed from its membrane, and all adhering albumen into another fimilar fpoon.. 

 They were each expofed to a heat above that of boiling water, coagulated and reduced; 

 nearly to drynefs, then left to cool, and twelve hours afterwards the filver remained untar- 

 niflied in both. 



A filver fpeculum placed in water, was adapted to receive the air contained in the follicu- 

 lus aeris, which remained expofed to this gas for two days, without any difcolouration. 



I mixed the albumen and vitellus together in a fpoon, and expofed them to heat without 

 difcolouring the filver. The intire albumen of a new laid egg was put into ten ounces (by 

 meafure) of boiling diftilled water in a glazed pipkin, and kept till it was coagulated; 

 firmly : a clean filver fpoon had been immerfed with the albumen, to which it adhered in 

 feveral places ; after fetting the veiTel in a cool place for an hour,, the filver. immerfed had 

 acquired a deep blue and brown colour, with various prifmatic (hades. 



An intire vitellus, freed from all other fubftances, was put into boiling water, together 

 with a filver fpoon as in the lafl defcribed experiment, but the filver did not receive any 

 tarnifli. 



Ten ounces by meafure of the water in which the albumen of on& egg had been boiled 

 was filtered,^ and put into a glafs veflel with a filver fpoon } after remaining there for two 

 hours it had received a deep copper colour. 



The fame quantity of water in which the vitellus of one egg had been boiled, was put 

 into a glafs with a filver fpoon, and remained fix hours without producing any change of: 

 colour. The water in the. two laft. experiments was at 60° ef Fahrenheit. . 



The 



