recognizing the Non-volatile Alkalies and Alkaline Earths. 329 



that it is met with in most laboratories as a reagent, is readily 

 diluted to the required intensity, and when so prepared will 

 keep good for some time. 



When the absence of potash has been ascertained by a method 

 which will be presently described, the above solution gives one 

 a means of rendering visible the red rays from lithia in the pre- 

 sence of soda, when the proportions do not exceed one part of 

 the former to a thousand parts of the latter. When potash is 

 viewed through this indigo solution red rays are likewise ob- 

 served, and these can be seen till the proportion of potash to 

 soda is less than one part to two hundred. To distinguish pot- 

 ash in the presence of soda or lithia, it was necessary to find a 

 medium through which no coloured rays from soda or lithia 

 would pass, but which would admit those peculiar to potash. This 

 was found to be a deep blue cobalt glass which I had cut up for 

 the purpose. Potash viewed through this glass gives to the 

 tlame an intense violet colour ; and this is still visible when one 

 part of potash is present with two hundred parts of soda. I 

 have not yet succeeded in getting a medium that will permit 

 rays from lithia to pass, and at the same time keep back all 

 those from soda or potash. But the presence of lithia can be 

 ascertained in that of potash, or of potash and soda, in the fol- 

 lowing way : — Place side by side in the flame two wires, one 

 having on its point a little pure sulphate of potash, and the 

 other the sample to be tested. If there be lithia in the sample 

 to the extent of one part to two hundred parts of potash, a very 

 marked difference will be seen between the colour of the two 

 flames, that containing lithia being of a much brighter red. 

 When soda, potash, and lithia occur together, one part of each 

 can be seen in the presence of two hundred parts of the mixture. 

 As soda in the minutest quantity is visible to the naked eye, we 

 have now a perfect means of separating the three alkalies from 

 one another. 



The following Table will show how the separation is best 



efiFected : — 



Mode of separating the Alkalies. 



With the naked eye. 

 Yellow : 

 Soda. 



Cobalt glass. 

 Violet-red : 

 Potash : 



Indigo solution. 



Comparative test with 

 pure sulphate of potash. 



Brighter red than sul- 

 phate of potash alone: 



Lithia. 



When the absence of 

 potash has been previ- 

 ously proved by the co- 

 balt glass, red rays visible 

 tliroiigh the solution 

 ])rove the presence of 

 litliia. 



