A. and F. Dupre : Spectrum-analysis of London Waters. 373 



still, if we would reconcile this with the other conclusions of 

 theory, we must give the equation the form 



a result which gives us no aid whatever in our search after a 

 finite root. 



4 Pump Court, Temple, London, 

 September 17, 1860. 



LI. Spectrum-analysis of London Waters. 

 By A. and F. Duphe*. 



HAVING been lately engaged in the analysis of several 

 London waters, we took occasion to examine them by the 

 recently published method of Bunsen and Kirchhoff; and since 

 this spectrum -analysis adds two new constituents (i. e. lithium 

 and strontium) to those already known, the results obtained may 

 not be uninteresting to some of the readers of the Philosophical 

 Magazine. If a small portion of the dry residue of any of the 

 waters examined is brought into the flame of an apparatus such 

 as described in Bunsen and KirchhofPs paper f, the lines Li a and 

 K a are seen with more or less distinctness as soon as the first 

 glare of the sodium and calcium spectrum is somewhat dimi- 

 nished. After the Li, K, and Na have volatilized, the calcium 

 lines come out with increased brilliancy ; and if the wire is now 

 dipped into HC1 and again brought into the flame, the lines Sr a 

 and Sr 7 are seen, as well as a very brilliant calcium spectrum. 

 The strontium lines come out generally with greater brilliancy if 

 the wire, before being moistened with HC1, is held for some time 

 in a reducing flame, easily obtained by closing the air-holes of 

 the Bunsen's burner. In some of the waters, especially the deep- 

 well waters, the line Li « is somewhat masked by the bright so- 

 dium and calcium spectra : it is, however, in all cases seen with 

 great distinctness if the residue of the water is treated with sul- 

 phuric acid and alcohol in the manner described by Bunsen and 

 Kirchhoff under the head of lithium. The strontium lines may 

 also be seen with great brilliancy on dissolving in hydrochloric 

 acid some of the crust deposited in boilers and kettles, and bring- 

 ing a drop of the solution into the flame of the apparatus. The 

 shallow waters appear to be rather richer in Li and Sr than the 

 deep-well waters ; the presence of Li in the latter can, however, 

 easily be demonstrated in an ounce or even in half an ounce of 

 the water. 



The following are the waters examined : — Thames water, taken 



* Communicated by the Authors, 

 t Phil. Mag. vol. xx. p. 89. 



