Wool in Relation to Science with Practice. 327 
considerable proportion of sulphur. E. Schulz further has shown that the 
portion of the yolk of wool, which is soluble in alcohol, consists principally of 
cholesterin, a peculiar well-defined fat. 
" Raw sheep's wool was also analysed in 1866 by Dr. Edward Heiden, who 
gives as its composition : — 
Moisture 10-443 
Fatty matters 27-018 
Mineral matter (ash) 1-028 
Sand 1-914 
Pure wool-fibre 09-597 
100-000 
or in a more detailed form the composition of raw wool is given by Dr. Heiden 
as follows : — 
100 parts contain : — 
Moistvu-e 10-443 
Fatty matters 27-018 
Pure wool 59-597 
Oxide of iron "181 
Lime -246 
Magnesia '060 
Potash -191 
Soda •027- 
Chlorine '008 
Carbonic acid * 031 
Phosphoric acid -031 
Silicic acid "253 
Sand 1-914 
100-000 
" It appears from Messrs. Marker's and Schulz's researches that raw wool 
contains both oil or fat in a free state, and fatty matters chiefly in combina- 
tion with potash, forming a kind of soluble soaj), which explains the loss 
in weight which -.vool sustains by the removal of the greater part of the fatty 
matter of raw wool. 
" Believe me, my Lord, yours faithfully, 
" Augustus Voelcker. 
"Plight Hon. Eael Cathcaet." 
TJie Yolk. — The quality of the wool is said to depend on the 
yolk ; hence the interest of the preceding information and of all 
investigations regarding its properties and effects. I should be 
glad to know chemically the essential difference between yolk and 
tallow : until now the subject has been neglected, and previously 
to my application to Dr. V oelcker, I knew not where to find any 
reliable chemical facts. All I could discover was that yolk is 
a soap of potash,* and compounds of potash with lime and animal 
matter, that imparts to wool its characteristic odour. The satu- 
ration with yolk gives wool the silvery lustre so much desired : 
how far can art supply this copious secretion, and what are the 
* Sheep are often washed in running-water, so that the valuable scouring 
properties of the yolk are lost. The greasier the water the whiter the wool. — 
Mr. Turner. See note, page 34G. 
