458 Intelligence and Miscellaneous Articles. 



contained therefore a gramme-equivalent o£ the ion Mn0 4 in 500 

 litres. The first four absorption-bands measured from red had the 

 same position iu 15 different salts of permanganic acid. 



2. Fluoresceine and its derivatives. — The solutions to be compared 

 were prepared in the same way as the permanganates, by decom- 

 posing solutions of barium salts of known strength with the 

 sulphates. 



(a) Fluoresceine. — The salts showed the same position of the 

 absorptiou-spectra with a strength of one gramme-equivalent in 

 4080 and the same position of the absorption-bands. 



(b) Eos hie. — In opposition to the observations of G. Kriiss 

 (Zeitsch. fur phi/s. Chem. ii. p. 320, 1888) and v. Knoblauch (Wied. 

 Ann. xliii. p. 767, 1891), all the salts investigated showed the same 

 absorption-spectrum. The author attributes this difference to the 

 different preparation of the specimens used. The salts which 

 the above-named experimenters had used were prepared by double 

 decomposition and purified by long continued washing. "With 

 eosine-alumiuium the author observed in the wash- waters on 

 continued washing a displacement of the absorption-bands towards 

 the side of the longer waves of light. Hence there are probably 

 two very similar compounds ; for example, two eosines isomeric as 

 regards the positions of the bromine atoms, the salts of which are 

 of different solubility. In the mode of preparation adopted by 

 Kriiss the more easily soluble part was removed, while in the 

 method which the author adopted the same mixture (if such there 

 was) in the same proportion was used. 



(c) Iodeosine.— There was the same absorption for the different 

 salts. If dilute solutions of aluminium sulphate and eosine-barium 

 or potassium are mixed the absorption-band is very feeble, and 

 disappears with any excess of aluminium sulphate. Hence the 

 aluminium salt of iodeosine is not probably present in the solution 

 as a regularly dissolved salt, but is probably present as a colloid 

 body. This conclusion is supported by the fact that the electrical 

 conductivity of a solution of 4000 litres is about 20 per cent, less 

 than that calculated for a mean value if iodeosine-potassium and 

 aluminium sulphate are brought together in equivalent quantities ; 

 whereas, for instance, with a mixture of eosine-potassium and 

 cadmium sulphate the value calculated is nearly obtained. 



(d) Dhiitrafluorescehis and (e) the tetrabrom- derivative of orcin- 

 phthaleine also confirm the conclusion drawn from the dissociation 

 hypothesis. 



3. Ilosolic acid. — Solutions were prepared which contained an 

 equivalent of the neutral salt in 2600 litres. Both by direct 

 observation and by photographs they showed considerable variations 

 in their spectra. The author ascribes this to an hydrolysis. "When 

 solutions were prepared by mixing the neutral solutions of barium 

 rosolate with barium hydrate equivalent to the barium they 

 contained already ; and when then quantities of the various 

 sulphates were added equivalent to the whole barium present, 



