Salts, colloidal peptisation

In preparing the membrane, a clear sol was obtained by the addition of acid into the aluminum sec-butoxide sol to peptise the sol and obtain a stable colloid solution. Aluminum monohydroxides formed by the hydrolysis of aluminum alkoxides, which are peptisable to a clear sol. Peptisation was performed by the addition of acid and heat treatment for a sufficient time. It was found that stable sols cannot be obtained when the concentration of the peptisation acid is too low. The critical range for inorganic acids such as nitric, hydrochloric and perchloric acids is 0.03-0.1 mole/mole of hydroxide. In this study, nitric acid was used as the peptising agent. The resulting sols are poured into Petri dishes and dried in an oven at a controlled drying rate to obtain a gel layer. The molar ratio of zirconia salt... 

The colloidal solution of sulphur so formed is treated with saturated salt solution when sulphur is precipitated. It is filtered, washed with water to remove salt and then washed further when the precipitate of sulphur peptises and forms a colloidal solution. 

The peptisation of most oxides, sulfides and salts may be explained on the same basis.- According to Graham the peptisation of ferric hydroxide hydrogel takes place on treating it with ferric chloride. One may assume that the ferric ion attaches itself to the ultramicrons of the colloidal ferric hydroxide, thus imparting to the latter the positive charge. 

Colloidal Salts. — In a great many other cases also the use of structural formulas serves to elucidate the processes and the reactions. In the chapters on colloidal salts other instances will be given. Here a single illustration will be taken up, viz the peptisation of cupric ferro-cyanide gel by potassium ferrocyanide. 

Colloidal titanic acid can be prepared by Graham s t method, viz., the addition of ammonia to salts of titanium in solution. The precipitate is peptised by nitric acid and then dialyzed. The dialysis of the nitrate, a method followed by Biltz,f is applicable to the preparation... 

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