Experiments on the Yolk of Wool. 35 



nothing but sulphate of lime. It differs, however, from it 

 in several respects; for example, it fuses much sooner in 

 the flame of the blow-pipe into a globule transparent while 

 in a state of fusion, but which becomes opake when fixed: 

 it is also much more soluble in water, and yet does not 

 contain acid in excess, as I fully assured myself. A solu- 

 tion of it in water precipitates abundantly muriate of barytes 

 and oxalate of ammonia : one of these precipitates is sul- 

 .phate of barytes, and the other oxalate of lime. The solu- 

 tion is rendered turbid neither by lime nor by ammonia. It 

 appears then that it is a modification of the sulphateof lime, 

 which is probably produced by the proportion of the ele- 

 ments. It is possible therefore that this salt may still con- 

 tain some portions of fat matter, which, by decomposing the 

 sulphate of lime and forming a little sulphuret, might faci- 

 litate the fusion. I regret that I had not a sufficient quan- 

 tity of this salt to examine its properties more in detail. 



The yolk of wool dissolved in water, when filtered, thick- 

 ened, and distilled with weak sulphuric acid, furnished a 

 liquor in which I readily distinguished the presence of the 

 acetic acid by its odour, its savour, and the properties of 

 the salts which it formed with different bases, and particu- 

 larly with lime and potash. This matter therefore contains 

 acetic acid, which, no doubt, is in part combined in it with 

 ,the potash. It contains also a little muriate of potash; for 

 it forms with the solution of silver an abundant precipitate 

 which is not entirely soluble in nitric acid, and it gives by 

 distillation with sulphuric acid sensible traces of muriatic 

 acid, which is found mixed with acetic acid. 



Yolk, when evaporated to dryness and strongly heated in 

 a silver crucible, swells up, becomes charred, and exhales 

 some foetid ammoniacal vapours ; oily fumes then arise, 

 which inflame, and when the greater part of the oil is dis- 

 sipated it becomes red and calmly fuses. At this period, if 

 it be poured on marble, a matter is obtained which becomes 

 fixed on cooling, has a grayish colour, and a very caustic 

 alkaline taste : if this substance be then dissolved in water, 

 nothing remains but an infinitely small quantity of carbona- 

 ceous matter, and the liquor, by evaporation, gives real 

 potash slightly carbonated. 



It results from these experiments that the oil or grease, 

 the presence of which in yolk has been proved by acids, is 

 combined with potash in the state of a real animal soap ; 

 that, besides, there is a portion of carbonate of potash if* 

 excess, since the acids produce in the solution of yolk, when 

 concentrated, a pretty strong spumous effervescence. Be- 



C 2 sides 



