COPRA A DANGEROUS COMMODITY ON SHIPBOARD.

Otago Daily Times, Issue 5803, 24 September 1880, Page 2

COPRA A DANGEROUS COMMODITY ON SHIPBOARD.

Tlie frequency with which shipments of copra heat and damage not only itself but the remainder of the cargo has induced 'the Committee of the Australian and New Zealand Underwriters' Association, London, to obtain a report on this substance from a skilled chemist. A copy of this report has been sent to U3, and we give it for the information of those concerned: —" I have carefully considered the various questions as to copra which were submitted in your favour of the Bth inst., and have also examined the sample of copra received with it. 1 have also, at various times, examined a large number of samples of copra, and am therefore familiar with the variations met with in commercial samples. Replying directly to your questions : Copra has a marked natural tendency to heating. It is practically impossible to store it in bulk for any length of time "without its heating-, unless it is periodically turned over, which is manifestly impossible in the case of a cargo. This ordinary or natural heating, as I may call it, doe 3 not often proceed to a temperature high enough to produce spontaneous ignition. I question, in fact, whether it would ever do so in the course of an ordinary voyage, unless some of the causes next to be referred to come into play, so as to increase the temperature. The tendency to heat is promoted to a marked degree by wetting-—i.e., every wetted sample is more likely to heat; and, in addition, it is almost certain that the degree of heat which is reached in the case of wetted samples is far higher than that which is reached with sound samples in good condition. Salt water would have greater power in promoting and increasing this heating than fresh water ; and it would have the further serious disadvantage of causing the wetted portion of tho cargo to absorb moisture again with every change of temperature, and thereby still further increase the heating tendency. "The tendency to heat is derendent to a considerable extent on the ripe or unripe condition of the nuts when harvested, and still more so on the employment of proper precautions in drying the broken pieces. Unripe or immature nuts are much more prone to decompose, and during this decomposition heating is produced. Careless dressing of the nuts in breaking, by which the pieces are left excessively or unduly wet with the milk or juice of the nut, will also very greatly assist and promote heating, as tliis milk is more prone to decompose than the dry substance of tho nut itself. Sun-drying is quite sufficient, if properly carried out. Kiln-drying would be certain to injuriously affect the article, and decrease its value. But if the partially sun-dried copra should become accidentally wetted, a more superficial drying again is not sufficient ; on the contrary, the nuts will then probably want more careful exposure to the sun, and more attention in turning over than the fresh nuts. The temperature at which ignition would take place depends on a variety of circumstances. To understand this, it must be borne in mind that copra contains a laige percentage of oil—4o percent., or upwards. Aa the nuts get heated, first gently and then more strongly, this oil, under the influence of the pressure and heat, begins partly to separate from the nuts, and then to absorb oxygen from the air and thus become more heated and volatile. Products are then given off which would probably ignite at a temperature of, say, 500 deg. F. (boiling water, 212 deg.). The nuts themselves would require at least 100 deg. higher temperature befere they actually fired ; but as against this, it must be remembered that one part being on fire the ignition of the rest wou'd soon follow. From all this it appears that a comparatively moderate heat for, say, three months may prepare the way for a very ready ignition as soon as tho temperature just passes a certain point, and that what this particular point may be—between, say, 500 and 600 deg., or even higher— will depend on the degree to which the slow decomposition has advanced. Ido not think the question of heat generated by surrounding cargo is of much moment, except in one case, and that is, that it is clearly undesirable to cover the copra with other cargo. It ought in every case, if practicable, to have a fairly uncovered top surface, so that when the hatches can be opened any vapour which may have been produced can escape freely. It is certainly safer to ship in bags than in bulk, because any tendancy to heat is much more readily localised. Ventilation to a moderate extent ia advantageous; but it would be a mistake to carry this too far. The practical summary, then, is :—The nuts should be ripe, harvested in suitable weather, carefully drained from the milk, well dried in the sun, carefully protected from wetting, still more carefully protected from salt water, and stowed so as to allow of moderate ventilation. If these precautions are taken, I think the risk of the heating of the cargo will be very much diminished.—G. W. Wioner, F.C.S., &c, &c."—Australian Shipping News.