Art. IX.—The Technical Analysis of Sliped Wool.
[Read before the Philosophical Institute of Canterbury, 4th November, 1908]
New Zealand exported in 1906 wool to the total value of £6,765,655, weighing 154,384,568 Ib. Of this, 15,049,470 lb., valued at £752,639, was sliped wool.
Sliped wool is the wool obtained from skins which have been washed in water to remove the adhering sand and dirt, together with a certain amount of the fat. After partially drying the skins in centrifugals the wool is removed by depilation and dried.
This is the process of treating the skins of sheep and lambs killed at the freezing-works in the Dominion. The sliped wool exported from New Zealand is almost exclusively a freezing-works product.
Two years ago a Royal Commission was appointed by the New Zealand Government to inquire into the cause of fires on wool-ships. Whilst some of the evidence taken before this Commission showed that fires had occurred in sliped wool, it could not be shown that this wool, either through excessive moisture or fat, had been the cause of fire.
In order to guard as far as possible against fires originating in sliped wool, either through excessive moisture or on account of foreign fatty matter, and, further, to obtain a standard quality for their output of wool, one of the largest meat-freezing and wool-export companies now requires that samples of wools from their various factories be regularly examined in then: chemical laboratory—determinations of moisture, natural wool-grease, other fatty matter, sand, dirt, and lime, and wool-fibre being made.
The methods of analysis in a works-laboratory must of necessity be rapid, but at the same time reasonable accuracy must be assured, otherwise the method is valueless.
As far as the author can find, no methods of wool-analysis requiring the above determinations have as yet been published, so the following methods were devised to meet the requirements of a works-laboratory in which the chemical control of wools is carried out.
All that is claimed for the following methods is that they meet the requirements of a works-laboratory, and that, while they give accurate results, they are rapid, and the condition of the wool can be reported before a consignment is baled for shipment.
Moisture is determined in 1 gram by drying in an air-oven at 110°, C. for one hour. After removal from the oven the sample must be placed in a desiccator under vacuum, and, after cooling, be weighed rapidly to prevent the absorption of atmospheric moisture, which, on account of the hydroscopic nature of wool, is readily taken up.
Natural wool-fat is determined in 2 grams of the material by extraction with hot alcohol. An aliquot portion of the liquid is evaporated to determine the total fat extracted; in another portion determine the free fatty acidity, using phenolphthalein as the indicator. After deducting the free, acidity from the total fats, the balance is considered natural wool-fat.
In another portion of the material extract the total fats, with petroleum ether, and after deducting the natural wool-fat the balance, is entered as “other fatty matter.” After drying the wool substance used in the previous determination, weigh. The sand, dirt, and lime may be approximately determined by shaking out mechanically the adhering particles after the total-fat extraction, and, after washing in hot alcohol and drying, the loss on again weighing is entered as sand, lime, and dirt. The remaining substance is wool-fibre, and is entered as such.
The following are examples of analysis of sliped wools carried out as described:—
[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]
|Per Cent.||Per Cent.||Per Cent.||Per Cent.||Per Cent.||Per Cent.|
|Other fatty matter||1.86||1.02||1.62||0.72||1.56||11.90|
|Sand, dirt, and lime||5.74||6.42||10.30||8.14||12.26||19.08|
It should be noted that scoured wools, or wools washed with, soap cannot; be examined for natural wool-grease by the method stated above, for the reason that all scoured wools retain some of the soap used, which is soluble in alcohol. The analysis of “thirds” shown above is an example of scoured wool.
For permission to publish these results I have to express my thanks-to the Christchurch Meat Company (Limited).