Between a shoulder, a, in the iron bolt and a shoulder in the porcelain cup, c, is placed an indiarubber ring, which forms a yielding washer and enables the cup to be screwed firmly to the bolt, while preventing FIG.
The stretching of the cell wall by the hydrostatic pressure is fixed by a secretion of new particles and their deposition upon the original wall, which as it becomes slightly thicker is capable of still greater extension, much in the same way as a thick band of indiarubber is capable of undergoing greater stretching than a thin one.
RUBBER, INDIARUBBER or Caoutchouc (a word probably derived from Cahucha or Gaucho the names in Ecuador and Peru respectively for rubber or the tree producing it), the chief constituent of the coagulated milky juice or latex furnished by a number of different trees, shrubs and vines.
" Rambong " or Assam rubber is the produce of Ficus elastica, commonly known as the indiarubber tree and cultivated in Europe as an ornamental plant.
In the industrial working of indiarubber, the various impurities present in the crude " wild rubber (bark, dirt and the principal impurities derived from the latex, except resin) are removed by the following process: The lumps of crude caoutchouc are first softened by the prolonged action of hot water, and then cut into slices by means of a sharp knife - generally by hand, as thus any large stones or other foreign substances can be removed.
It must, however, be distinctly understood that it is not the mere admixture but the actual combination of sulphur with indiarubber that causes vulcanization.
Cut sheets, or articles made from them, may be saturated by being laid in powdered sulphur maintained for some hours at about 110° C. Sheets sulphured in this way can be made up into articles and joined together either by warming the parts to be united, or by means of indiarubber solution; after which the true vulcanization, or " curing," as it is termed, can be brought about in the usual way.
Indiarubber stereotypes are now extensively made use of as hand stamps, and attempts have been made to introduce them for press and machine printing.
The ordinary macintosh or waterproof cloth is prepared by spreading on the textile fabric layer after layer of indiarubber paste or solution made with benzol or coal-naphtha.
The articles are first fashioned by joining the soft material; they are then varnished, and afterwards cured in ovens heated to about 135° C. The fine vulcanized " spread sheets " are made by spreading layers of indiarubber solution, already charged with the requisite proportion of sulphur, on a textile base previously prepared with a mixture of paste, glue and treacle.
Weber, The Chemistry of Indiarubber (London, 1902); Selected papers from the Kew Bulletin, iii.
The tube is made of glass, indiarubber, copper or lead, according to the liquid which is to be transferred.
Although even good membranes of copper ferrocyanide are rarely perfectly semi-permeable, and in other membranes such as indiarubber, &c., which have been used, the defects from the theoretical values of the equilibrium pressure are very great, yet, in the light of the exact verification of theory given by the experiments described above, it is evident that such failures to reach the limiting value in no wise invalidate the theory of osmotic equilibrium.
Gardeners often dispense with the pot, using sphagnum moss and leaf-mould only when propagating indiarubber plants, perpetual carnations, dracaenas, &c.
The apparatus consisted of two small boards, with glass rollers between them, the whole fastened together by indiarubber bands in such a manner that the upper board could slide under lateral pressure to a limited extent over the lower one.
Between the hook or crank (e) and the centre of the upper screw (a a), the indiarubber in a state of torsion (f) extends.
The late Sir Benjamin Baker, F.R.S., suggested that the stresses might be measured by experiments with elastic models, and among others, experiments were carried out by Messrs Wilson and Gore a with indiarubber models of plane sections of dams (including the foundations) who applied forces to represent the gravity and water pressures in such a manner that the virtual density of the rubber was increased many times without interfering with the proper ratio between gravity and water pressure, and by this means the strains produced were of sufficient magnitude to be easily measured.
- Diagrams illustrating results of Wilson and Gore's experiments with an Indiarubber model dam.
It is navigable for a period of about five months of the year, when the Purus valley is inundated; and, for the remaining seven months, only canoes can ascend it sufficiently high to communicate overland with the settlements in the great indiarubber districts of the Mayutata and lower Beni; thus these regions are forced to seek a canoe outlet for their rich products by the very dangerous, costly and laborious route of the falls of the Madeira.
The finest quality of indiarubber comes from the Acre and Beni districts of Bolivia, especially from the valley of the Acre (or Aquiry) branch of the river Purus.