Author Description

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1878 Excerpt:...as electrodes; secondly, they are very bad conductors. A piece of fire-brick, held in the nippers, will give no spectrum; the Bpark jumps over it in the most clevor way, and gives nothing but the spectrum of the nippers, be they brass or steel. Some of the small tubes were made--they are shown at fig. 2390 in the diagram. The object here was to bury the electrode in the pounded fire-brick, and force the current to pass through it. These are obviously a modification of Gbisslbb's tubes. The lines of silica and alumina shine out with splendour, but they do not last long, the glass gets coated with the material which is decomposed by the spark, and forms a conductor, the spark only passing in fitful flashes, and giving but very little light; on the whole, the best way of charging the tube is, to allow the platinum electrode to come through the throat of the tube, and burying the lower electrode in the powder under examination. This has the further advantage that the Bpectrum of the glass itself does not intrude; the lines of the platinum must, of course, be noted, and not confused with those of the powder. The spectra of iron ores come out very well by this method. The nozzles a b (fig. 2393) are for letting in gas. This being the most difficult spectrum with which the author has had to deal, he has thought it better to explain it before proceeding to phosphorus, which forms the main subject of the paper. The phosphorus lines were got in this way--a small hole was drilled into a piece of carbon and filled up with phosphorus, the phosphorus worked over the carbon like the head of a rivet, so that the spark could not get from one carbon electrode to the other without volatilising the phosphorus; but it is quite obvious that this method would not do in atmospheri...