Chemistry and Physics. 399 



at first, then finally for 2 hours at the full heat of a Bunsen 

 burner. During the heating the mass must be frequently stirred 

 with a strong platinum wire, and it is advisable to place the cru- 

 cible in a hole in an inclined piece of asbestos board during the 

 ignition, in order to protect its contents from the sulphur of the 

 flame. After cooling, the mass is extracted with water, the solu- 

 tion is filtered, the residue is boiled with sodium carbonate solu- 

 tion and finally washed with water. The solution is acidified 

 with hydrochloric acid, evaporated to dryness to separate silica, 

 and the sulphur finally determined as barium sulphate in the 

 usual manner. The author states that in this way he has obtained 

 very good results more conveniently and quickly than by the 

 usual methods, and he gives test analyses upon copper pyrites, 

 iron pyrites, and mercuric sulphide which show very satisfactory 

 results. — Berichte, xlv, 869. h. l. w. 



5. Benzoic Acid as an Acidimetric Standard. — Although the 

 employment of organic acids for this purpose is not new, it is 

 interesting to notice that G. W. Moeet has used benzoic acid 

 with very satisfactory results. It was found best to fuse the 

 bulky sublimed acid before weighing by heating it in a platinum 

 dish to about 140° C. The fused material can then be broken up 

 and kept indefinitely for use. Phenol phthalein was used as the 

 indicator with the careful exclusion of carbonic acid. The mate- 

 rial has the advantage of high molecular weight, so that compara- 

 tively large quantities can be used, thus reducing the errors in 

 weighing. It is also easily obtained in a pure condition, it is 

 stable and not hygroscopic. — Chem. J¥ews, cvi, 66. h. l. w. 



6. Ein neuer Fall von Koppelung kurz- und langwelliger 

 Fluoreszenzbanden . — According to Stark's theory of band spectra 

 two kinds of absorption bands are to be distinguished. The 

 criterion for differentiation depends on the behavior of the bands 

 when the attempt is made to stimulate fluorescence. The so-called 

 long-wave bands have the property of absorbing light without 

 appreciable fluorescence. On the other hand, absorption of light 

 by a " short-wave" band is, in general, accompanied by the emission 

 of fluorescent light not only in its own interval of wave-lengths 

 but also in the region of the " coupled " long-wave band. 

 Furthermore, the absorption is more intense for the short-wave 

 bands than for thte associated long-wave bands. 



It has been shown by Steubing that mercury vapor affords a 

 practical example of coupled absorption bands. The discovery of 

 three other concrete cases by M. Gelbke is obviously a matter of 

 theoretical importance. The substances which he has shown to 

 possess coupled absorption bands are acetone (CH 3 COCH s ), 

 diacetyl (CH 3 COCOCTI 3 ), and ethylencyanid-monoxal-ethylester 

 (N 2 H 3 C 4 COC0 2 C 2 H 6 ). These ketones were dissolved in very 

 pure ethyl alcohol. 



The source of light employed was a strong spark between elec- 

 trodes made of an alloy of iron and tungsten. The condensing 

 lens was of quartz and the spectrograph had fluorite objectives 



