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Rh to which phenomena should be subjected has been unduly discouraged. For example, the apparently physical phenomena of lubrication have been reduced by the observations especially of W. B. Hardy and of Langmuir to terms of chemical structure and of function as determined by molecular structure. A single layer of molecules is sufficient to cover and cloak a surface a matter of importance to be borne in mind in considering the action of catalysts and the disposition of the molecules is determined by their structure. Thus the spread of a liquid upon water is determined by the affinity of the substance for water but this is a localized function of its structure. Langmuir's measurements show that, in the case of the complex fatty acids, the molecules are to be thought of as having only the terminal carboxyl groups " dissolved " or dipping down into the water, the complex hydrocarbon group sticking up much as does a fisherman's float. Molecules so placed, ranged side by side in piles, would present an upper surface composed of the terminal methyl groups (CHs).

W. B. Hardy's measurements show that the lubricating effect of substances is definitely a function of molecular structure; it therefore varies with the nature of the surface to which it applies, as both the affinity of substance to surface and inter- molecular affinity are functions of the structure of the substances. Much has been done of late, especially by Jacques Loeb, to show that chemical conceptions can be applied in explanation of the peculiar " physical " properties of colloid materials and that the behaviour of these is comparable with that of crystal- loids when determined under proper conditions. The passage of colloid materials from the dissolved to the undissolved particulate state and the accompanying changes are certainly matters to be considered from the point of view above explained.

Most irregular results have been obtained by several workers who have studied the effect of different acids on various proper- ties, such as viscosity and osmotic efficiency, of liquids containing gelatin or egg albumin ; as a rule, acids have been used in equiva- lent concentrations, without taking their relative efficiencies into account. Loeb has shown that there is no difference in the effects of a variety of acids when the solutions of the protein acid are of the same acid efficiency (the same pH value) and the same concentration of the originally isoelectric protein. The same is true of alkalies. The proteins exist in three states, by derivation from the aminocarboxy-acids: either the molecule may be neutral or it may be either acidic or basic. Thus, if brought into contact with a salt at apH = 4-7, gelatin is neutral; but at apH < 4-7, it forms an acid salt, whilst if the pH be >4'7, a metallic salt is formed.

Not only are more precise conceptions of the behaviour of colloids being formed by such studies but light is also being thrown on the characters of the acids. W. B. Hardy, in 1907, pointed out that the solvent power for globulin of strong and medium acids is measured by the number of gramme-molecules present, not by the number of gramme equivalents. He wrote HC1 = H 2 SO4=H3PO 4 ; adding, "very weak acids have a lower solvent power HCl=5HA = 3ooo H 3 BoOa. These rela- tions are explained by the very weak basic functions of globulin." Loeb has obtained results of the same order. Using gelatin and egg albumin, he has found that most acids act as monobasic molecules not only phosphoric acid but also the organic dibasic acids, succinic and tartaric, even tribasic citric acid; oxalic acid, however, was intermediate in behaviour be- tween the mono- and di-basic acids; sulphuric acid was definitely dibasic, serving to couple two molecules. That oxalic and the other organic acids should act as monoacids sulphuric.

The whole question of effective acidity is one requiring further study it may be questioned whether any inorganic acid be more than monobasic in the proper sense of the term.

Benzenesulphonic acid (CeHsSOsH) and similar acids have about 90% of the hydrolytic efficiency of sulphuric acid; it would therefore seem probable that this acid is to be regarded as an unsymmetrical hydroxysulphonic acid rather than as

Q H (cf. Proc. Roy. Soc., 1914, 90, 73).

Progress in Industrial Chemistry. Chemistry is a constructive as well as an analytic science, touching our life at every point: In it is embodied our knowledge of the materials of which the world consists and the office of its priests is to make clear the manifold activities of these materials. The science is fundamental to all our industries ; the key to our own nature and acts may even- tually be found within its precincts. How much our insight is deepening, our outlook widening, how much the science is gain- ing in precision, the previous sections of this article may have shown; in the following, the attempt is made to trace out the main lines along which specific advance is taking place.

The progress in industrial chemistry, in recent years, has been very marked. Even in the oldest of chemical industries, the heavy chemical trade, so called, which includes the manufacture of alkali and of sulphuric, nitric and muriatic acids, as well as bleaching-powder and soap, great changes have been effected.

Sulphuric acid has been made to an ever-increasing extent, especially since the outbreak of the World War, by the " Con- tact Process " by associating sulphur dioxide directly with atmospheric oxygen, by means of a finely divided platinum used as a catalyst. When the usual raw materials were not available, a process was worked out, in Germany, in which calcium sul- phate was roasted in a rotatory kiln, together with silica, clay and powdered coal thus producing sulphur dioxide; the residue was used for cement manufacture.

During the war nitric acid was produced for the first time on a large scale by the direct oxidation of ammonia again with the aid of platinum as a catalyst. The special factory erected for its manufacture was constructed in six months, at a cost, it is said, of 4,000,000. Another synthetic process of making nitric acid is that of Birkeland and Eyde, developed at Notodden, in Norway, since 1903, which involves the application, on a large scale, of Cavendish's fundamental discovery that nitric oxide may be produced by passing an electric discharge through air (see NITROGEN FIXATION). The world is, therefore, now independent of the natural supply of nitrate in the form of Chili saltpetre.

The manufacture of caustic soda and potash by the elec- trolysis of a solution either of salt or of potassium chloride, has been carried out on an ever-increasing scale; as a consequence, chlorine has been produced, in considerable quantities, together with hydrogen. More chlorine having been made than could well be used in the manufacture of bleaching-powder, the first steps have been taken towards preparing muriatic acid directly from chlorine and hydrogen. The production of chlorine, in excess of the normal requirements, was probably the primary cause of its use in the World War. Another consequence has been the introduction of a variety of chlorinated compounds, e.g. chlorinated ethanes and tetrachlorethylene, as solvents.

Even in the ammonia-soda process changes are foreshadowed. This process involves the treatment of a solution of salt contain- ing ammonia with carbon dioxide and the production of sodium bicarbonate, together with ammonium chloride. The custom has been, after separating the carbonate, to recover the ammonia by distilling with magnesia, allowing the magnesium chloride to run to waste. Now that ammonia is likely to be procurable in large quantity, the more rational course would seem to be to separate the ammonium chloride as such and use this as an agricultural fertilizing agent in place of ammonium sulphate thus saving sulphuric acid.

The manufacture of ammonia directly from atmospheric nitrogen and hydrogen, through the agency of a catalyst, under a pressure of between 200 and 300 atmospheres, has been carried out, on a large scale, in Germany, during several years past; in fact, there seems to have been over-production. Latterly, a modified process, at a much higher pressure (1000 atmos- pheres), has been developed by the French engineer Claude.

Another process of making ammonia, now fully developed, involves the production first of calcium carbide, CaCj, by heating a mixture of lime and anthracite coal in an electric furnace; then the conversion of this carbide, by direct absorp- tion of nitrogen, into calcium cyanamide, CaCN 2. This latter interaction takes place at a moderate temperature and with