482 



NATURE 



[December 31, 1914 



of publication by the Government of Assam. Of 

 these and of the valuable "Gazetteer of Upper 

 Burma and the Shan States," by Sir J. G. Scott 

 and Mr. J. P. Hardiman, Colonel Shakespear has 

 made much use. But his own experiences have 

 enabled him to add interesting material, and the 

 large collection of photographs and drawings adds 

 to the value of the book. It has passed the censor 

 attached to the Headquarters staff in India, and 

 it is creditable to that department that they have 

 not suppressed the outspoken criticisms on our 

 methods in the past of dealing with these trouble- 

 some neighbours. We have been too prone to 

 delay action for the punishment of raids, to impose 

 inadequate penalties on the guilty tribes, to use 



Fig. 2. — Angami Nagas. From " History of Upper Assam, 

 Upper Burmah, and Norili- Eastern Frontier." 



large and expensive expeditions to effect what 

 might have been, and has been, done by smaller 

 detachments. Hence, we have met with many 

 regrettable incidents which by prescience and 

 better management might have been avoided. 



The publication of the book is timely because it 

 impresses the need of a firm policy on this 

 frontier, particularly as China is beginning to 

 show her power. If the new Republic succeeds in 

 organising an army capable of meeting disciplined 

 troops we may have trouble before us. To meet 

 this emergency the extension of our railway system 

 to the strategical points on the frontier is an 

 obvious necessity. 



NO. 2357, VOL. 94] 



COLLOIDAL CHEMISTRY IN RELATION 

 TO INDUSTRIES.^ 



II. 



P'RACTICALLY the only inorganic colloidal 

 -'- preparation made on a large scale at present 

 is the colloidal graphite manufactured by Acheson 

 and used as a lubricant under the name of "Aqua- 

 dag." Colloidal tungsten was at one time em- 

 ployed in the manufacture of squirted filaments 

 for incandescent lamps, but these have been super- 

 seded by drawn wire. The use of colloidal 

 sulphur as spray for hops and vines has been 

 patented and seems likely to be more efficacious 

 than the coarser suspensions of flowers or milk 

 of sulphur. 



Of far greater technical importance, however, 

 than these colloidal preparations of inorganic sub- 

 stances are the bodies which, to the layman, arc 

 exclusively suggested by the terms "Colloids" or 

 the colloids of Graham. This class comprises 

 such important constituents of organic raw- 

 materials as albumen, hide substance, starch, and 

 cellulose ; also the various derivatives of the latter, 

 india rubber, gutta percha, and, finally, many 

 manufactured products, among w^hich glue and 

 gelatin may be mentioned as typical. These 

 various substances naturally exhibit a somewhat 

 bewildering variety of individual behaviours, and 

 it is therefore impossible to do more than refer to 

 some properties they possess in common. 



Most of them in contact with water — or, in the 

 case of india rubber and nitrocellulose, in contact 

 with certain organic solvents — exhibit the pheno- 

 menon of swelling, i.e. they imbibe the liquid 

 with increase in volume. The process may either 

 come to an end without solution or dispersion, as 

 with cellulose, or it may proceed as far as the 

 latter either at ordinary or higher temperature, as 

 with albumen and gelatin respectively. This 

 swelling is obviously an inevitable concomitant or 

 antecedent of any treatment with liquids, and 

 therefore of importance in processes differing as 

 widely as tanning and malting. It is w^ell known 

 empirically that the amount of water taken up 

 is affected by even small concentrations of acid, 

 alkali, and neutral salts. The important fact 

 brought out by colloidal research is that this 

 action, particularly in the case of neutral salts, 

 is in no sense chemical, since it is the same on 

 substances differing as widely as gelatin and agar. 

 This knowledge has already been of great value 

 in elucidating the rationale of many empirical pro- 

 cesses, and its systematic application is likely to 

 be far-reaching. Particularly interesting is the 

 effect of iodides and thiocyanates, which promote 

 the absorption of water to such an extent that, 

 for instance, gelatin dissolves in cold .solutions of 

 such salts, and that cellulose (as has been shown 

 by v. Weimarn) can be dissolved in hot solutions 

 of calcium iodide or thiocyanate. 



A further general rule is that solutions of all 

 these bodies, whatever their nature or that of the 

 solvent, exhibit two peculiarities : the physical 



1 Continued from p. 422. 



