SCIE VCE-GOSSIP. 





i \ COLOl RING OF BIRDS' I • 



i: . Reg in u i> J. 1 iii .11 1.-,. 



r \\ VS verj pleo Mr. Wheldon's remarks 



in youi i \nte, p. 200) and 



welcom isms, as il is only by threshing out 



h as he raises, that we may h- .p<_- 



un anj satisfactory result in this enquiry. 

 1 think, it I understand Mr. Wheldon rightly, he 

 rather doubts that iron is actually present in the 

 pigment of feathers or eggs, and it is evidently 

 extremely desirable that we should have a >ati 

 chemical proof of il 1 isl an 1 I hi mall quantity 

 ol pigment on an egg, and its intimate admixture 

 with the calcium carbonate ■>! the shell, renders it 

 tn discover by a chemical test whether a 

 particular dark markingiscaused by anoxide, carbonate, 

 or chloridi ol in m. \ el 1 hi pr enci - iron in some 



tpable "I 1 f. 1 think I have 



ded in demonstrating this by the following 

 experiments. 



Pour hydrochloric acid upon the brown pari of any 

 deeply mark those of gulls, grouse, or 



terns. The brown pigment is at once turned to a 



1 -en, and a liquid of the latter colour mixes 

 with the carbonic acid bubbles, liberated from the 

 shell. Add a drop or two of a strong solution "I 



am ferricyanide, and the green is intensified, 

 a red or brown precipitate being very often formed, 

 which can be increased by pouring a little inure 

 acid on to the heap "f bubbles. To produce this 

 precipitate in the greatest abundance, mix a lew- 

 drop.-, ul the ferricyanide with a little of the 

 acid, taking care that the latter is considerably in 

 excess. Pour the mixture on an egg. Then, repeat 

 the experiment, taking less acid in proportion, so as 

 to produce a green, containing red or brown particles. 

 Remove some of this coloured liquid from the egg 

 and heat cautiously on glass by the side of a candle 

 Same, or the egg itself can be heated, if it is thick 

 As the liquid dries several precipitates are 

 formed, bin among them is Prussian blue, 



thus the existence of iron in the pigment is fully 

 demonstrated. The hydrochloric acid has formed 

 protochloride of iron with the iron on the shell, and 

 the ferricyanide of potassium has precipitated it as 

 Prussian blue. Of the other precipitates, one 

 is white and is probably calcium chloride 

 formed by the action of the acid on the shell, and 

 the other is the red or brown substance above 

 described, which, when red, has become brown by 

 heating. These two latter often form a crust over 

 some of the blue, more of which can lie found by 

 scraping them away. Touch one of the brown lumps 

 with a drop of potassium ferrocyanide, more Prussian 



blue is formed, and we ■ that it must be 



chloride of iron. It is not unlikely I 



would be fot med by an 'lie acid. 1 



cyanide, will not I I'm jan blue with th 



substance, il added before i> 



diately combines with the free acid, some ol which i> 

 always unavoidably present, to form white potassium 

 chloride; these flakes and hydrocyanic acid can 

 easily be distinguished. The hydrochloric acid is 

 driven off by heating. 



I am inclined to think thai there is - >me substance 

 present in the pigment of all eggs that prevents the 

 ferricyanide from at once combining with the green 

 proto-chloride, but which is also vaporised when 

 heated. This might account for the chloride being 

 green instead of yellow brown, like most chlorii 

 iron. Citrates, we know, disguise the effect of 

 ferricyanide on iron in much the same way. This 

 can be confirmed in a somewhat curious mannei bj 

 taking any coloured bivalve shell — a dark oyster, 

 especially the inside surface, will do very well. Pout 

 on it some hydrochloric acid, a yellow liquid will 

 be formed. Then add a little potassium ferricyanide. 

 a surprising amount of Pridian blue will b 

 duced. Evidently the liquid is a perchloride of iron, 

 and the pigment ol these molluscs' shells contains 

 iron. I believe, from observing the effects pi 

 that the colouring matter is pure or nearly pure 

 oxide of iron, [f another mollusc's shell is taken and 

 ferricyanide used instead of ferrocyanide. a green 

 liquid precisely similar to that produced on e| 

 formed, and by carefully arranging the proportion of 

 acid we can obtain the brown precipitate as before. 

 I In blue can be shown to be Prussian blue, both in 

 the case of eggs and mollusc shells, by adding 

 . or a solution of ammonia. The former 

 -. the colour and the latter turns it purple, as 

 is the case with ordinary Prussian blue. Having 

 the presence of iron in the dark pigment on an 

 I think it will be readily admitted thai 

 it is most likely to be in the form of a carbonate or an 

 oxide, on. at any rate, the eggs of all but sea-birds. 

 Both these substances form chloride of iron with 

 liloric acid. The fact that when some of the 

 pigment is extracted from even the most intensel; 

 coloured eggs ol ( lass 1. as described in my previous 

 article, it never shows the least sign of being attracted 

 by a magnet, unless healed, is strong evidence that in 

 this case il is carbonate of iron, and not oxide. 1 

 have not succeeded in extracting any colouring matter, 

 in ils natural condition, from eggs of Class 5, so 1 have 

 nol been able to lest if it is capable of attraction. 



