This short account of the vulcanising properties of plantation rubber would not be complete without a reference to Fine Hard Para, the premier rubber of the Amazon. This rubber has come to be regarded as the standard high-grade product with which plantation rubber may be compared, and many manufacturers are still of the opinion that it is unsurpassed by any plantation product. Yet, when subjected to the ordinary vulcanising tests, we find that samples of Fine Hard Para give figures very similar to average plantation rubber; indeed, it is not difficult to find specimens of plantation rubber which give appreciably higher figures on testing. It is claimed, however, that Fine Para is more uniform than plantation rubber, and can be relied on always to give the same results. Yet tests on a series of Fine Hard Para specimens gave variations in rate of cure similar to those found for plantation. Some figures were published, which tended to show that the variation was smaller for Fine Para, but it turned out that each of the samples taken for examination consisted actually of a number of slices cut from different balls, so that greater uniformity was not unexpected.[58] The superiority of Fine Para is, therefore, somewhat of a mystery. It is probable that some manufacturers prefer to use it because they feel safer with it, and know actually how it will behave from long experience. In one respect Fine Para is possibly superior to most plantation rubber--that is, for the preparation of raw rubber solution for sticking the seams of waterproof garments, and for similar purposes. The method of preparation may well influence the strength of the raw rubber when used for this purpose. Plantation rubber has been prepared in the same manner as Brazilian Para, in particular on an estate in Java. The product resembles Brazilian Para in appearance. Vulcanising tests gave satisfactory figures, but, as already stated, this would not serve to show that the rubber was equal to Brazilian Para from the manufacturer's standpoint. [58] Bulletin R.G.A., September, 1920, p. 347. INDEX Acetic acid, 74, 279 Acid, acetic, 74, 279 --, carbonic, gas, 289 --, formic, 279 --, hydrochloric, 282 --, hydrofluoric, 282 --, mixing, with latex, 79 --, nitric, 282 --, oxalic, 279 --, pyroligneous, 282 --, quantity of, 76 --, sulphuric, 279, 286 Acids for coagulation, effect of, on rate of cure, 323 --, quantities necessary for modern requirements, 78 Air-drying, aids to normal, 143 --, of crepe, rate of, 138 --, progress of, 140 Alcohol, coagulation with, 289 Alum, coagulation with, 282 Anti-coagulant for transport, 61 Anti-coagulants, 46 Artificial driers, 133, 148 Ash on sheet, 276 Assembling cases for shipment, 156 Bags for packing, 154 Bakau, 147 Bales for packing, 154 Bark in crepe, 232 -- -- shavings, 56, 123 -- -- sheet, 276 Bases in vulcanised rubber, 322 Basket plants, 10