The determination of combined carbon in iron and steel by the colorimetric process

Mecltanics, Pl~ysics, and C]teraistry.

356

THE DETERMINATIONOF COMBINEDCARBONIN IBONAND STEEL BY THE COLORIMETBICPROCESS, BY J. BLODOET BRITTO~¢~ of the Iron-Mas'~ers' Laboratory.

Loh'G ago Professor Eggertz, of Fahlun, Sweden, called the attention of metallurgical chemists to the fact that when pure metallic iron is dissolved in nitric acid, of common strength, the solution, ff not too conccntrated, is colorless or nearly so, but when steel or iron containing carbon in combination is substituted for the pure metal the solution is colored, and the shade varies exactly in proportion to the amount of carbon present ; and, based upon this fact, he suggested a method whereby carbon determinations, sufficiently accurate for many commercial purposes, could be made with facility. Several modifications of this method have been proposed. One of them, affording exceedingly accurate results, has been in use at the Iron Masters' Laboratory for some time. Instead of a single tube containing a standard solution for comparison, as suggested by Eggertz, a number of tubes having their solutions differently standardized, one from the other, are employed. These are arranged securely in a walntlt-wood frame with spaces between for placing the tube containing the solution to be tested, and forming together a convenient portable instrument called a colorimeter--an exact representation of such an instrument is-here annexed. The position of the tube containing the solution to be tested is shown at A. A JI

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The tubes are 8 of an inch in diameter and 3½ inches in length, filled with water and alcohol colored with roasted coffee and hermetically sealed. The solution inthe tube to the lef~ has its color to correspond exactly with one produced by 1 grin. Of iro'n:containing "02 per cent. oi" combined carbon dissolved in 15 C. C. of nitric acid. The solution in the tube next to it has its.color to cor. respond with one produced by the same quantity of iron but containing •04 per cent. of combined carbon, and so with each of the other tubes, increasing "02 per cent, of carbon in regular succession

358

Mechanics, Physics, and Chemistry.

water and alcohol, as suggested by Eggertz, answers well ; but with roasted coffee as the coloring matter I have succeeded in obtaining the true shades. I must say, however, that this latter solution has not been in use sufficiently long to allow me to positively assert that its color will not change after some length of time. As a rule the instruments are kept in the dark except when in actual use, and no perceptible change has yet taken place.

ILLUMINATED FOUNTAINS. BY PROFESSOR HENRY MORTON) PH.D.

I~" a previous number of this Journal, Vo]. LV., page 206, I gave a description of a simple and effective arrangement for illus. trating the total reflection of light in the interior of a liquid vein. In another form a less theoretically interesting, but more beautiful, illuminated fountain may be arranged as follows, the description being taken from one which I used in one of my lectures at the Franklin Institute, during the Winter before last. On a light table about 3 feet 6 inches in height, is placed a shallow basin, or pan of tin, six feet in diameter and about 2½ inches deep, supported by a skeleton framing of wood. Around the edge of this basin is placed a ring of ~ inch lead pipe provided with 50 vertical jets, each of i inch aperture turned slightly inward. Towards the centre is a ring of similar pipe 18 inches in diameter, also provided with 50 similar vertical jets inclined slightly outwards. Both pipes are connected with the water supply but controlled by separate stop cocks. When operating together they form a beautiful pyramidal sheaf of spray (in the case just mentioned) 15 feet high and 6 feet in diameter at the base. The jets are each attached by a short piece of ~ inch lead tube which allows of their ready adjustment in direction. So much for the fountain, we next come to the arrangements for illumination. On the lower part of the table-frame which supports the basin is arranged an ordinary magic lantern with its condensers in its roof, protected by an inclined plate of glass, directing the ascending stream of heated gases to a crooked chimney of 1½ inch tin pipe. Immediately above these condensers is an opening through