* 
ON COLLOID CHEMISTRY AND ITS INDUSTRIAL APPLICATIONS. 3 
Grimaux!® showed that glycerine prevents the precipitation of 
hydrous ferric oxide by caustic potash. 
If one ion of an electrolyte is adsorbed more than the other ion, 
it will tend to peptise the adsorbing material and to give rise toa 
colloidal solution containing positively or negatively charged particles 
according to the nature of the adsorbed ion. Univalent ions are not 
all adsorbed alike ; nor are bivalent or trivalent ions. The order of 
adsorption is specific with each substance. Certain univalent ions 
are adsorbed by certain substances more than certain bivalent or 
trivalent ions.2? In many cases there is, however, a marked tendency 
to increased adsorption with increasing valence, as formulated in 
Schulze’s so-called law.?!_ It seems to be a general rule that insoluble 
electrolytes adsorb their own ions markedly. Consequently, a 
soluble salt having an ion in common with a sparingly soluble elec- 
trolyte will tend to peptise the latter. 
Freshly precipitated silver halides are peptised by dilute silver 
nitrate or the corresponding potassium halide,”? the silver and the 
halide ions being adsorbed strongly. Many oxides are peptised by 
their chlorides or nitrates, forming so-called basic salts.2*> Sulphides 
are peptised by hydrogen sulphide.** Gelatine is liquefied or peptised 
by a potassiun iodide solution. The peptisation of hydrous oxides 
by caustic alkali can be considered as a case of common ion or as the 
preferential adsorption of hydroxyl ion.2» Hydrous chromic oxide 
gives an apparently clear green solution when treated with an excess 
of caustic potash ; but the green oxide can be filtered out completely 
by means of a collodion filter, a colourless solution passing through.”® 
Hantzsch”’ considers that hydrous beryllium oxide is peptised by 
caustic alkali, copper oxide is peptised by concentrated alkali,?* and 
so is cobalt oxide.*? In ammoniacal copper solutions part of the copper 
oxide is apparently colloidal and part is dissolved.*” Freshly precipi- 
tated zinc hydroxide is peptised by alkali; but the solution is very 
instable, the zinc hydroxide often coagulating inside of half an hour. 
The relatively small amount of zinc remaining in solution is 
present chiefly or entirely as sodium zincate.*! The bulk of the 
19 Comptes rendus, 98, 1485, 1540 (1884). 
*0 Bancroft, Jour. Phys. Chem. 19, 363 (1915). 
21 Schulze, Jour. prakt. Chem. (2), 25, 431 (1882); 2'7, 320 (1884). 
#2 Lottermoser, Jowr. prakt. Chem. (2) 60, 341 (1903); '72, 39 (1905); 78, 374 
(1906) Zeit. phys. Chem. §2, 371 (1908). 
23 Miller, Ber. deutsch. chem. Ges, 39, 2856 (1906); Zeit. anorg. Chem. 52, 316 
(1907). Szilard, Jour. Chim. phys. 5, 488, 636 (1907). Graham, Jowr. Chem. Soc. 
15, 254 (1862). 
*4 Spring, Ber. deutsch. chem. Ges. 16, 1142 (1882). Prost, Jour. Chem. Soc. 54, 
653 (1888). Winssinger, Bull. Soc. chim. Paris (3) 49, 452 (1888). Linder and 
Picton, Jour. Chem. Soc. §1, 116 (1892). Meunier, Comptes rendus, 124, 1151 (1897). 
Young, Jour. Phys. Chem. 21, 1, 14 (1917). 
25 Bancroft, Jowr. Phys. Chem. 20, 99 (1916). 
36 Fischer and Herz, Zeit. anorg. Chem. 31, 352 (1902). Fischer, Zeit. anorg. Chem. 
40, 39 (1904). _ Nagel, Jowr. Phys. Chem. 19, 331, 569 (1915), 
7 Zeit. anorg. Chem. 3Q, 289 (1902). 
28 Loew, Zeit. anal. Chem. 8, 463 (1870). Fischer, Zeit. anorg.' Chem. 40, 39 (1904). 
*9 Tubandt, Zeit. anorg. Chem. 45, 368 (1905). 
% Peligot, Ann. Chim. Phys. (3) 68, 343 (1861). Guignet, Comptes rendus, 55, 
741 (1862). Grimaux, Comptes rendus, 98, 1434 (1884). 
31 Hantzsch, Zeit. anorg. Chem. 30, 289 (1902) ; '75, 371 (1912); Fischer and Herz, 
Zeit. anorg. Chem. 81, 352 (1902) ; Klein, Zeit, anorg. Chem. 94, 157 (1912). 
20895 A2 
