348 Scienitfic [ntelligence. 



the permanganates for example, solutions containing the molecu- 

 lar mass in grams of the ion Mn0 4 in 500 liters of water, give 

 the same values for the absorption bands whatever the base. 

 On the arbitrary scale employed, the four bands of potassium 

 ])ermanganate for example, were at 2600, 2697, 2803 and 2913 ; 

 the positions of these bands in the twelve other permanganates 

 examined not differing more than two or three units from these. 

 In further proof of the fact that with this degree of dilution the 

 metallic permanganates are completely dissociated, photographic 

 reproductions of the several spectra are given side by side, in 

 the paper, these spectra being identical for the different salts em- 

 ployed. The same conclusion was found to be true of the salts 

 of fluorescein with sodium, lithium, benzylamine, potassium, 

 methylamine, ammonia, piperidine, dipropylamine and trimethyl- 

 amine; and also of the salts of eosin, both blue and yellow, of 

 iodeosin, of dinitrofluorescein, of orcinphthalein and its tetra- 

 bromine derivative, of rosolic acid, of diazoresocin, of diazoreso- 

 rufin, of safrosin and of the chromoxalates. To show that the law 

 is equally true for positive ions as for negative the author gives 

 the results obtained with the salts of para-rosaniline, aniline- 

 violet, chrysaniline and chrysoidine, twenty different non-colored 

 acids being employed. Generalizing from 300 cases examined 

 the author regards the fact as established, that in dilute solutions, 

 salts having the same colored ion give identical absorption spec- 

 tra; the few exceptions being readily accounted for, either by 

 the formation of insoluble compounds or by the hydrolysis of 

 salts having feeble acids or bases. — Zeitsehr. physik. Chem., ix, 

 579; J. Chem. Soc, lxii, 1137, Oct. 1892. G. F. b. 



3. Affinity-coefficients of Acids. — The relative affinities of a 

 number of acids have been measured by Lellmann and Schlie- 

 manjt by means of a spectrophotometry method. This method 

 is as follows: A measured quantity (25 co ) of a solution of two 

 milligram-equivalents (0 - 448 grms.) of pure metahydroxyanthra- 

 quinone in a liter of 96 per cent alcohol, is mixed with a definite 

 quantity of a solution of known strength of the pure barium 

 salt of the acid, the mixture diluted to 50 cc and examined with the 

 spectrophotometer ; its absorption being compared with that of 

 a solution of the same quantity of metahydroxyanthraquinone in 

 excess of barium hydroxide. The alcohol and the water used in 

 the preparation of the solutions are both carefully purified from 

 basic substances by distillation over potassium hydrogen sulphate 

 and even the glass vessels in which the solutions are kept are 

 carefully freed from alkali by prolonged digestion with dilute 

 sulphuric acid. In cases where the barium salt is not sufficiently 

 soluble the potassium salt is employed. The results are given in 

 terms of a constant k • this constant expressing the fact that 

 when in the alcohol-mixture employed, equal equivalents of 

 metahydroxyanthraquinone, of a given acid and of the base are 

 contained, and when k equivalents of the salt of the acid are 

 formed to one of a salt of metahydroxyanthraquinone, this fact 



