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~Colorimetric Assays.~--These are assays in which the colour imparted to a solution by some compound of the metal to be determined is taken advantage of; the depth of colour depending on the quantity of metal present. They are generally used for the determination of such small quantities as are too minute to be weighed. The method of working is as follows:--A measured portion of the assay solution (generally 2/3, 1/2, 1/3, or 1/4 of the whole), coloured by the substance to be estimated, is placed in a white glass cylinder standing on a sheet of white paper or glazed porcelain. Into an exactly similar cylinder is placed the same amount of re-agents, &c., as the portion of the assay solution contains, and then water is added until the solutions are of nearly equal bulk. Next, a standard solution of the metal being estimated is run in from a burette, the mixture being stirred after each addition until the colour approaches that of the assay. The bulk of the two solutions is equalised by adding water. Then more standard solution is added until the tints are very nearly alike. Next, the amount added is read off from the burette, still more is poured in until the colour is slightly darker than that of the assay, and the burette read off again. The mean of the readings is taken, and gives the quantity of metal added. It equals the quantity of metal in the portion of the assay. If this portion was one-half of the whole, multiply by two; if one-third, multiply by three, and so on. When the quantity of metal in very dilute solutions is to be determined, it is sometimes necessary to concentrate the solutions by boiling them down before applying the re-agent which produces the coloured compound. Such concentration does not affect the calculations.

In this manner we continued to improve our situation by "exchanging" with every canoe we met which happened to be better than our own, until finally our princely friend ordered a gay party of merry-makers out of a fine large skiff, which they cheerfully "exchanged" for our leaky canoes and departed singing happily, feeling honored indeed that this opportunity had come to them to serve the great chief Ratu Pope Seniloli; and thus suffering qualms of conscience, we sailed to our destination leaving a wake of confusion behind us. Moreover I forgot to mention that many natives had by Ratu Pope's orders been diverted from their intended paths and sent forward to announce the coming of himself and the "American chiefs." Thus does one of the Royal house of Mbau proceed through Fiji.

The Darwinian doctrine of evolution depends essentially on _the cumulative augmentation_ of minute variations in the direction of utility. But can such minute variations, which are undoubtedly continually appearing among the individuals of the same species, possess any selection-value; can they determine which individuals are to survive, and which are to succumb; can they be increased by natural selection till they attain to the highest development of a purposive variation? To many this seems so improbable that they have urged a theory of evolution by leaps from species to species. Koelliker, in 1872, compared the evolution of species with the processes which we can observe in the individual life in cases of alternation of generations. But a polyp only gives rise to a medusa because it has itself arisen from one, and there can be no question of a medusa ever having arisen suddenly and _de novo_ from a polyp-bud, if only because both forms are adapted in their structure as a whole, and in every detail to the conditions of their life. A sudden origin, in a natural way, of numerous adaptations is inconceivable. Even the degeneration of a medusoid from a free-swimming animal to a mere brood-sac (gonophore) is not sudden and saltatory, but occurs by imperceptible modifications throughout hundreds of years, as we can learn from the numerous stages of the process of degeneration persisting at the same time in different species.

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