54 J. L. Smith on determining the Alkalies in Minerals. 
phuretted hydrogen, a test most readily performed by means ofa 
piece of lead paper. The liquid is thrown on a filter to separate 
the sulphuret of lead; the filtrate containing the alkalies as 
acetates, is evaporated, and when nearly dry, an excess of hydro- 
chloric acid is added, and the whole evaporated to dryness over 
a water-bath, and finally heated to above 500°. A hot solution 
of the chlorid of lead can be used instead of the acetate, render- 
ing the addition of hydrochloric acid unnecessary. 
34, It needs but little experience to convince one of the 
superiority of this method, over that by the chlorid of baryum, 
for converting the sulphates into the chlorids, its principal re- 
commendation being the indifference with which an excess of the 
lead salt can be added, to precipitate the sulphuric acid, and the 
subsequent facility with which that excess of lead can be got rid 
of. It may be well to state, that experiments were made to prove 
the perfect precipitation of the sulphuric acid from the sulphates 
of the alkalies by the salts of lead, and it is only after numerous 
comparative results, that it is now recommended. 
To distinguish the Alkalies from each other when mixed. 
35. To distinguish potash, soda and lithia when mixed, is 
attended with more or less difficulty, according to the proportions 
in which they are mixed ; of the three, potash is the most easily 
recognized, next in order is soda, and lastly. lithia; the presence 
of which, mixed in small amount with proportionally large quan- 
tities of the other alkalies, it is almost impossible to decide on 
with any accuracy, without direct separation. 
36. In the analysis of many minerals, the characters of which 
lead to the supposition of the presence of the alkalies, it is useless 
to precede the quantitative determination by one of a qualitative 
character, especially as the steps to be followed to separate the 
alkalies are the same in both cases, and to proceed in this way, iS 
economy of time. ‘rom my own experience concerning the con- 
stitution of the silicates, there are doubtless but a very few of 
them without an appreciable quantity of alkalies in their cov- 
* The alcoholic solution does not give perfect results and should not be used. 
