Colloid chemistry by Alexander Jerome 1876-

Author:Alexander, Jerome, 1876- [from old catalog]
Language: eng
Format: epub
Tags: Colloids
Publisher: New York, D. Van Nostrand company
Published: 1924-03-25T05:00:00+00:00

1907, 4, 428^31; J. S. C. I., 1907, 703) qiiinone renders gelatin inBoluble.

The fact observed by Fickenday (J. Landw., 1906, 54, 343) that more alkali is reqiiired to flocculate natural clay soils than kaolin suspensions, he attributes to the protective action of the humus present {see Keppeler and Spang-enberg, J. Landw., 1907, 56, 299).

A. S. Cushman, in hia excellent work upon the use of feldspathic rock as fertilizer (U. S. Dept. of Agriculture, Bureau of Plant Industry, Bulletin No. 104; Cushman and Hubbard, J. Am. Chem. Soc, 30, 779), has shown that the fine grinding of feldspar increases the amount of potash available under the action of water. Thus, a coarse powder having an area of 43 sq. cm. per cc. of solid feldspar yielded 0.013 per cent, whereas a fine powder whose area was 501,486 sq. cm. per ec. yielded 0.873 per cent of potash and soda. These fine particles averaged about 0.1 ii in diameter, which is relatively large as compared with colloidal dimensions; but under the action of physical and chemical soil agencies they undergo further disintegration, finally reaching a colloidal condition in which still more of

their potash is available, a condition favored and maintained by the organic protective colloids of the soil.

With these brief and inadequate remarks we must dismiss this subject of such vast importance and fascinating interest, referring to the extensive literature, much of which is quoted in Bulletin No. 52 and the other publications of the Biireau of Soils.

El-BCTROPLATING AND EleCTK ODE POSITION OF

Metals. — The addition of protective colloids to electroplating baths tends to the production of fine-grained non-crystalline deposits. A. G. Belts in a paper entitled "The Phenomena of Metal Depositing" (J. Am. Electrochem. Soc,

1905, 8, 63) has shown that there are many factors influencing the action of the colloid, and has suggested a number of possible explanations. The correct explanation, however, has been given by Muller and Bahntje (Z. Elektrochem., 1906, 12, 317; J. S. C. I.,

1906, 484) who state that the added colloid keeps the deposited metal (copper) in an amorphous, non-crystalline condition, gelatin producing the most powerful effect, egg albumen considerably less, whiia si'O^ «s^^

starch have comparatively little action. They also found that the deposited copper weighed about 0.2 per cent more than under normal conditions, indicating that some of the colloid had been carried down with the metal.

The relative efficiency of the eoUoids just referred to corresponds to their relative efficiency in protecting from coagulation solutions of colloidal gold (see Zsigmondy, J. S. C. I., 1902, 192; also CoUoids and the Ultraroicro-scope, p.. 81), which is additional evidence that we have another instance of protective colloidal action, by which the crystalhzation forces of the metal are powerfully influenced.

Metallurgy. — Since coarsely crystalhne metals are brittle, tending to split along the lines of crystal cleavage, various physical and chemical means are employed in technical practice to obtain a hard, fine-grained structure. (See I. Langmuir, Iron & Steel Inst., Sept. 1907; J. S. C. I., 1907, 1094.) Among the

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