CHEMISTRY. 



the blue crystalline crust is drained, and the 

 excess of sulphuric oxide drawn off, at a tem- 

 perature not nbove that of the blood. The 

 bluish -green crust thus obtained is very friable, 

 and resembles malachite lit structure. It de- 

 composes, without fusion, slowly at common 

 temperatures, but more rapidly on heating, 

 evolving sulphurous oxide, and leaving sulphur 

 behind. Its formula is S a Ot, and it is named by 

 the author sulphur-sesquioxide, ordithionic ox- 

 ide. No compounds of it have yet been made. 

 Sulphur as a Mordant. C. Lauth having 

 published the discovery that finely-divided sul- 

 phur, as precipitated from solutions of hypo- 

 sulphites, is a good mordant for methyl green, 

 Dr. Isidor Walz and Mr. Charles M. Stillwell 

 have made a series of experiments to deter- 

 mine whether sulphur would act in a similar 

 manner with other dye-stuffs. An account of 

 these experiments is given in the American 

 Chemist as follows: The first dye-stuff tried 

 was eosin. Some sodium hyposulphite was 

 added to an aqueous solution of eosin in a test- 

 tube, and, after addition of a few drops of hy- 

 drochloric acid, the liquid wa* neutralized with 

 ammonia. On standing a short time, a veri- 

 table lake of sulphur and eosin settled to the 

 bottom as a rosy-pink precipitate. Next a 

 piece of woollen fabric was dyed with eosin. 

 The result again showed that sulphur acts as a 

 mordant for eosin, and the resulting shade is 

 somewhat different from that obtained by 

 omitting the sulphur, as shown by a simul- 

 taneous dyeing test. This result induced the 

 authors to test the behavior of wool, mordanted 

 with sulphur, toward madder. A u swatch " 

 from the same piece, but not mordanted, was 

 placed in the dye-bath at the same time, in 

 order to facilitate comparisons. In the bath 

 prepared with French extract of madder, the 

 mordanted wool took a full reddish-brown 

 shade, while the non-mordanted cloth was but 

 slightly stained. To decide whether this col- 

 or was due to the alizarin or to purpurin, 

 samples of mordanted and clean wool were 

 treated in baths mounted with artificial aliz- 

 arin on the one hand, and with commercial 

 purpurin on the other. The samples from 

 the alizarin bath were alike, and dyed a good 

 yellow ; those from the purpurin bath showed 

 a light reddish-brown, the color of the mor- 

 danted sample being deeper than the other. 

 Hence it appears that sulphur does not act as 

 a mordant toward alizarin, but does act in 

 that manner toward purpurin or the other 

 coloring principles of madder. The authors 

 Miled their experiments to cochineal, log- 

 wood, redwood, and fustic ; but, in the case of 

 these dye-stuffs, they discovered no difference 

 between the colors produced on ordinary and 



1 sulphur-mordanted wool. 

 Varying Composition of the Waters of the 

 Nile. The annual flood in the Nile begins 

 toward the end of May, the increase in size 

 being at first exceedingly gradual. In June it 

 is just perceptible, and the river goes on in- 



creasing in volume till abont the middle of 

 September, when it usually attains its greatest 

 size. At Christmas the water i- low a^uin, 

 and the same level remains till May. Prof. J. 

 Alfred Wanklyu has published the following 

 tabular statement of the composition of Nile 

 water ill different months : 



What is specially worthy of note in this 

 table is the great relative alteration in the pro- 

 portion of chlorine : that, whereas in the 

 beginning of June the chlorine amounts to 1.8 

 grain per gallon, it sinks to 0.3 grain when the 

 river has attained a great size, and remains at 

 very little above that proportion until the end 

 of the year. In marked contrast with the 

 variableness of the chlorine is the comparative 

 constancy of the hardness. These phenomena 

 become intelligible when we reflect on the 

 conditions under which the river is placed : 

 " The water which swells the Nile in the latter 

 half of the year is storm- water, being thick 

 and muddy. Storm-water sweeps over the 

 surface of the country, without penetrating 

 far below, and we may very readily under- 

 stand that such water, passing over a country 

 long ago denuded of salt, should carry little or 

 no salt into the Nile, which it dilutes, and so 

 causes it to contain only an exceedingly mi- 

 nute proportion of chlorine. By about Christ- 

 mas, the storm-water had ceased flowing into 

 the Nile, which, during the spring half-year, 

 must be fed with water which has passed 

 deeper into the ground, and which has under- 

 gone concentration by evaporation, in addition 

 to having washed extensive strata, from which, 

 doubtless, it extracts chlorine. We can easily 

 understand how the Nile should become more 

 chlorinous as the spring advances, and how 

 the chlorine should be at the maximum just at 

 the beginning of flood-time. The hardness, on 

 the other hand, being due mainly to carbonate 

 of lime, we can understand that, from the 

 slightness of its solubility, the carbonate of 

 lime, and consequently the hardness, should be 

 under totally different conditions from the 

 chlorine." 



No doubt, other rivers would, on examina- 

 tion, show similar though minor fluctuations. 

 The importance of recognizing the different 

 causes to which fluctuation of chlorine in 

 drinking-water is due will be obvious when it 

 is considered how great a stress is laid upon 

 the presence of chlorine as an index to sew- 

 age contamination. 



