Wright. — Absorption of Moisture hij Wools. 223 



It is probable that the fatty matter forms a film over the surface of the 

 wool, and, being itself impervious to moisture, thus retards to a certain 

 extent the moisture-absorption by the fibre and the other constituents of 

 the wool. 



Another point of considerable interest in connection with the foreign 

 fatty matter present iu slipe wool is that it is an oxidizable fat, and it is pro- 

 bably this fat wliioh caused the rise in temperature in certain of the bales 

 of wool experimented upon by the Wool Fires Commission,* Nos. 6 and 12. 



In this connection it is of interest to refer to the reports by Mr. R. J. 

 Friswell and Dr. J. S. Haldanef on these experiments. 



Mr. Friswell states, " Another most interesting point is the fact that 

 the oxidation of the grease by air and moisture (to which I attributed the 

 fires on the s.s. " Gothic ") is proved by these experiments. I have ex- 

 tracted the grease from Nos. 6 and 12, and have found it oxidized, and 

 rubber- or varnish-like in character." Dr. J. S. Haldane states, " The 

 results of the tests quoted in your letter are, I think, very instructive. They 

 seem to me to point to this : that the rise in temperature of the bales was 

 due to some substance (probably an oil) capable of combining with oxygen 

 at a comparatively low temperature, and so producing heat ; that the 

 amount of this substance is very small, since the process practically comes 

 to an end after about a fortnight, and that more or less of this substance 

 was present in all the bales tested.'' 



This fatty matter has been found in greater or smaller amounts in all 

 slipe wools examined, but the amount present, while it is undoubtedly 

 capable of producing heat by oxidation in the presence of air and moisture, 

 is relatively so small that even should oxidation take place the heat gene- 

 rated cannot be very great. Where the amount of foreign fatty matter is 

 high, of course a very serious danger does exist, as, for instance, in the 

 case of a wool containing only from 6 to 10 per cent, moisture, but from 

 34 to 36 per cent, foreign fatty matter of an oxidizable nature. J 



Summary. 



The results of this investigation show that the amount of moisture 

 which a wool can absorb from the atmosphere depends on several factors. 



1. The relative humidity of the atmosphere determines the amount of 

 moisture which a dry wool will absorb, more moisture being absorbed during 

 a period of high relative humidity than when the humidity is low. 



2. Pure wool-fibre, of which greasy wool contains from 50 to 70 per cent., 

 and slipe wool about 75 per cent., can absorb from 18 to 20 per cent, of its 

 weight of moisture from the atmosphere. This amount is not sufficient to 

 account for all the moisture absorbed by the dry normal wool-fibre. 



3. Natural wool-fat, present in greasy wool in amounts up to nearly 

 17 per cent., and in slipe wool to about 6^ per cent., is capable of absorbing 

 about 17 per cent, of its weight of atmospheric moisture. 



4. Suint, or wool-perspiration, can absorb from 60 to 67 per cent, of its 

 weight of moisture when exposed to the atmosphere, this matter being very 

 hygroscopic, and is present in greasy wools in amounts up to nearly 13 per 

 cent., and in slipe wools to about 2 per cent. 



* Kept. Comm. on Fires on Wool-ships, Exhibit 40, p. Ixxxvii. 

 t Supji. Rcpt. Comm. on Fires on Wool-ships, p. 6. 



% Re})t. Comm. on Fires on Wool-ships, p. Ixxxv ; Journ. Soc. Chem. Ind., \o\. xxvii. 

 No. 13. 



