THE COLLOID-CHEMISTRY OF SOAP MANUFACTURE 193 



Group III. 



(A) Potato flour, tapioca meal, starches and seed husks. 



(B) Clay, barytes, asbestos, chalk and solutions of magnesium 

 salts (?) 



From a colloid-chemical point of view, it is easiest to dispose 

 of the third group first. With the exception of magnesium sul- 

 phate (which might more correctly be placed in the first group) 

 all the substances used are earths or carbohydrates which, as 

 employed, are largely colloid and possessed of a considerable 

 capacity for hydration. As such they are therefore only materials 

 which, when mixed with the soap, increase the volume of what is 

 sold to the public as soap. This does not mean, of course, that, 

 under certain circumstances, the sandlike properties of some of 

 these fillers may not be of service or actually necessary in various 

 washing processes. Since the washing properties of soaps are in 

 large measure associated with their properties as hydrated col- 

 loids and as such properties are more or less common to all hy- 

 drated colloids whether inorganic (hydrated clays) or organic 

 (swollen starch grains), this fact may, of course, also be empha- 

 sized. But unless the composition and such merits or demerits 

 of the material which is sold to the public as soap are clearly 

 stated, the motives behind their use cannot be held to be higher 

 than those always incident to mere substitution. 



With the market price of sugar what it is, the use of this 

 material as a filler cannot be charged to any desire to increase 

 yield while decreasing cost of production. The soaps may be 

 " loaded " with the sugars (which carry with them not only high 

 specific gravity but also a certain amount of water), yet the 

 real reason for their use seems now to be that they give increased 

 transparency to the product. How the sugars accomplish this 

 is not yet settled. The sugars do not at any concentration 

 " salt-out " the soaps so that any combination of the sugar with 

 the solvent (as so frequently discussed in the case of tin- salts) 

 must either be decidedly less or of a different type. The sugars 

 clarify soap/water systems as do alcohols or aldehyds, which 

 prompts us to the conclusion that they have an action like the 

 last-named materials and so really owe their effects to the fur- 

 nishing of such a substitute " solvent " for the pure water more 

 rommnrilv pn-srnt in soap. 



In tin- substances of the first group, we deal throughout with 



