CHEMISTRY. (CHEMICAL PHYSICS.) 



99 



was found that the concentrations of the solu- 

 tions which are just sufficient to check the de- 

 velopment of the cells completely are much 

 smaller in the case of the strong acids like hydro- 

 chloric and sulfuric acids than in the case 

 of weak acids, such as acetic and butyric acids. 

 The results led the author to conclude that the 

 antiseptic power is essentially determined by the 

 hydrogen ion which is contained in the solution, 

 and that the electrolytic dissociation theory is 

 competent to account for the observed phenom- 

 ena in a satisfactory manner. As is required 

 by this theory, it is found that the addition of 

 neutral acetates to a solution of acetic acid dimin- 

 ishes the antiseptic power of the acid; the con- 

 centration of the active component of the solu- 

 tion, the hydrogen ion, being under these circum- 

 stances reduced to a much smaller value. 



In a lecture at the Royal Institution, Prof. Otto 

 N. Witt, of Berlin, explained that in order to 

 become a dyestuff a substance must not only 

 be so intensely colored that it could communi- 

 cate its own shade to colorless substances hold- 

 ing it in solution, it must not only be soluble in 

 water or other liquid suitable for preparing a 

 dye-bath, but it must also be soluble, and even 

 much more soluble than in water, in the colloid 

 which forms the substance of the textile fiber. 

 The finished dyed fabric is nothing more or less 

 than a solid solution of the dyestuff in the sub- 

 stance of the fiber, unless there are chemical in- 

 fluences, such as that of the mordants, at work 

 to change the solution into a suspension by pre- 

 cipitating the dyestuff after its immigration 

 into the fiber. This peculiar combination of 

 solubilities is rare in colored substances of an 

 inorganic nature; and in the vast domain of or- 

 ganic substances of the aliphatic series few dye- 

 stuffs are met with, but in the aromatic series, 

 where the power of selective absorption of light is 

 very frequent, it would be curious if they were 

 not of common occurrence. Since the physical 

 properties of every compound are direct func- 

 tions of its molecular constitution, it is easy to 

 believe that this peculiar combination of solu- 

 bilities would be the result of certan general 

 conditions fulfilled in many members of the aro- 

 matic group ; and the theory the author had pro- 

 posed twenty-five years before was simply an 

 attempt to discover those conditions by inves- 

 tigating the constitutional peculiarities of all 

 those dyestuffs whose constitution was known 

 in those days. In the molecule of every coloring- 

 matter whose constitution was known certain 

 atomic constellations had been observed which 

 seemed to be essential, and of which two must 

 always be present chromophores and auxo- 

 chromic groups. Of the former, about two 

 dozen were known, all agreeing in the fact that 

 they could not exert their influence except in the 

 presence of the auxochromic groups, of which 

 very few were known. There must exist a law 

 governing the formation of chromophoric groups, 

 but so far it has not been definitely established, 

 though some progress has been made toward 

 doing so. Our knowledge of the chemical causes 

 of the physical properties of coloring-matters is 

 continuously developing, and lately some definite 

 views have been formed about the connection of 

 the chemical constitution of the aromatic bodies 

 with that form of selective absorption of light 

 known as fluorescence. Much work has been 

 done on the constitution of the azo-colors, the 

 introduction of which was the direct result of 

 early efforts to conduct the. search for new color- 

 ing-matters on definite scientific principles. The 

 number of dyestuffs of this class is extraordi- 



nary; and it has been computed that 3,150,000 

 different ones are at present easily accessible. 

 Of these, at least 25,000 are patented, while 

 more than 500 are manufactured on the larger 

 scale. Azo-dyestuffs can be produced at will 

 to dye wool or silk or cotton, to dye slowly or 

 quickly, to stand soap, or acid, or alkali; and 

 this possibility of adjusting their properties 

 with almost mechanical precision has been the 

 cause of the greatest successes of the color in- 

 dustry. While this field has borne it rich harvest, 

 other fields have not been neglected. Perhaps 

 the greatest and most brilliant success of the 

 chemistry of dyestuffs has been the industrial 

 synthesis of indigo. 



An experimental basis has been laid for the 

 chemical theory of the formation of petroleum 

 by the researches of MM. Paul Sabbatier and 

 J. B. Senderens on the action of reduced nickel, 

 iron, and other metals upon hydrocarbons. By 

 the direct hydrogenation of acetylene in the 

 presence of nickel these authors have obtained 

 liquid mixtures of hydrocarbons which can be 

 made to correspond with the American or Cau- 

 casian petroleum by varying the conditions of 

 the experiment. To account for the formation 

 of petroleum, it is thus sufficient to admit that 

 there are in the depths of the ocean free alkali 

 metals and metallic carbids which in contact 

 with water give rise to mixtures of hydrogen 

 and hydrocarbons. These cases encounter nickel, 

 cobalt, or iron in a finely divided state, and 

 thus give rise to the mixtures of hydrocarbons, 

 so as to form natural petroleum. Berthelot and 

 Mendeleef had supposed that the natural hydro- 

 carbons were mainly formed by the action of 

 steam upon metallic carbids; but difficulty had 

 been found in applying this theory to the forma- 

 tion of the naphthas of the Russian oil-fields. 



Chemical Physics. It was found in the ex- 

 periments of E. Rutherford and F. Solly, of 

 McGill University, that thorium from which the 

 radio-active constituent (Thx) has been sepa- 

 rated regained its activity with time, while the 

 activity of Thx decreased with time. Thx was 

 observed to possess a distinct chemical behavior 

 which differentiated it from thorium. Ammonia 

 was the only reagent of those tried capable of 

 separating it from the latter. Experiments are 

 cited which indicated that Thx was continuously 

 produced by thorium compounds at a constant 

 rate. The rate of production of Thx and rate 

 of decay of its activity were apparently unaf- 

 fected by known agencies. Both changes pro- 

 ceeded independently of the chemical and phys- 

 ical conditions of the molecule. The source of the 

 energy required to maintain the radio-activity 

 of thorium over indefinite periods was therefore 

 supposed to be found in a chemical change pro- 

 ducing new types of matter. Emanating power 

 appeared to be a property of Thx, and not of 

 thorium, and was proportional to the activity 'of 

 the Thx present. The decay and recovery of 

 the emanating power of Thx and thorium were 

 completely analogous to the decay and recovery 

 of radio-activity. These results find their sim- 

 plest explanation in the view that one of the 

 products is gaseous and in the radio-active state 

 is .the emanation. The result arrived at, that 

 radio-activity is the consequence of changes in 

 which new types of matter are formed, leads to 

 the conclusion that it is the result of subatomic 

 changes. In experiments made after the writing, 

 of this account, solution in water was found to 

 increase the emanating power of thorium nitrate 

 nearly two hundred times, and solutions of thori- 

 um chlorid gave a large amount of emanation. 



