Analysis by Spectrum-observations. 105 



from all the others by the green lines Ba a and Ba /3 (which are 

 by far the most distinct) appearing the first and continuing 

 during the whole of the reaction. Ba 7 is not quite so distinct, 

 but is still a well-marked and peculiar line. As the barium spec- 

 trum is considerably more extended than those of the other 

 metals, the reaction is not observed to so great a degree of 

 delicacy ; still 0*3 grm. of chlorate of barium burnt with milk- 

 sugar gave a distinct band of Ba a which lasted for some time, 

 when the air of the room was well mixed by moving an open 

 umbrella about. Hence we may calculate, in the same manner 

 as was done in the sodium experiment, that about y^ws °^ a m *Ui- 

 gramme of barium salt maybe detected with the greatest certainty. 



The chloride, bromide, iodide, and fluoride of barium, as also 

 the hydrated oxide, the sulphate, and carbonate, show the reac- 

 tion best. It may be obtained by simply heating any of these 

 salts in the flame. 



Silicates containing barium, which are decomposed by hydro- 

 chloric acid, also give the reaction if a drop of hydrochloric acid 

 be added to them before they are brought into the flame. Baryta- 

 harmotome, treated in this way, gives the lines Ca ex. and Ca /3, 

 together with the bands Ba a and Ba /?. 



Compounds of barium with fixed acids, giving no reaction 

 either when alone or after addition of hydrochloric acid, should 

 be fused with carbonate of sodium, as described under strontium, 

 and the carbonate of barium thus obtained examined. If 

 barium and strontium occur in small quantities together with 

 large amounts of calcium, the carbonates obtained by fusion are 

 dissolved in nitric acid, and the dried salt extracted with alcohol. 

 The residue contains only barium and strontium, both of which 

 can almost always be detected. When we wish to test for small 

 traces of strontium or barium, the residual nitrates are converted 

 into chlorides by ignition with sal-ammoniac, and the chloride of 

 strontium is extracted by alcohol. Unless one or more of the 

 bodies to be detected is present in very small quantities, the 

 methods of separation just described are quite unnecessary, as is 

 seen from the following experiment : — 



A mixture of the chlorides of potassium, sodium, lithium, 

 calcium, strontium, and barium, containing at the most T ^- of a 

 milligramme of each of these salts, was brought into the flame, 

 and the spectra produced were observed. At first the bright 

 yellow sodium line Na a appeared, with a background formed by 

 a nearly continuous pale spectrum. As soon as this line began 

 to fade, the exactly defined bright red line of lithium Li « was 

 seen ; and still further removed from the sodium line the faint 

 red potassium line Ka a was noticed, whilst the two barium lines, 

 Ba Uj Ba 0, with their peculiar form, became visible in the proper 



Phil Mag, S. 4. Vol. 20. No. 131. Aug. 1860. I 



