DETERMINATION OF ALKALIES IN MINERALS. 209 



preferring the Berlin porcelain) of about three and a half to 

 four inches diameter, inverting a clean funnel of smaller diam- 

 eter over it, and evaporating to drjniess on the sand-bath or 

 over a lamp. I prefer the latter, as at the end of the operation 

 the heat can be increased to four or five hundred degrees. 



27. By this operation, which requires no superintendence, 

 one hundred grammes of sal ammoniac might be separated 

 as easily and safely as one gramme from five milligrammes 

 of alkalies, and no loss of the latter be experienced. What 

 remains in the capsule occupies a very small bulk. This is 

 now dissolved in the capsule with a. little water (the funnel 

 must be washed with a little water), small quantities of a solu- 

 tion of carbonate of ammonia added, and the solution gently 

 evaporated nearly to dryness. This is done to separate what 

 little lime may have escaped the first action of the carbonate 

 of ammonia, or may have passed through the filter (22) in 

 solution in carbonic acid. If any of the earths soluble in car- 

 bonate of ammonia existed in the mineral, those now become 

 separated along with the lime. 



28. A little more water is now added to the contents of the 

 capsule, and the w^hole thrown on a small filter ; the filtrate as 

 well as washings- are received in a small porcelain capsule. 

 The liquid contains only the alkalies (as chlorides and nitrates), 

 mixed with a minute quantity of sal ammoniac. This is evapo- 

 rated to dryness over a water-bath, and then heated cautiously 

 over the lamp to drive off what sal ammoniac may have formed 

 (27), which is exceedingly minute if the process as pointed out 

 be closely adhered to. It is not absolutely necessary to heat 

 the capsule over the lamp to get rid of the sal ammoniac, for 

 the little sulphate of ammonia which may be formed in the 

 next step is easily removed in the final heating in a platinum 

 vessel. 



29. On the contents of the capsule, as taken either from the 

 water-bath or as after being heated over the lamp, pure dilute 

 sulphuric acid is poured (1 part acid, 2 water), and the contents 

 boiled for a little time, when all the nitric acid and chlorine in 

 combination with the alkalies will be expelled ; the acid solu- 

 tion of the alkalies is now poured into a platinum capsule or 

 crucible, evaporated to dryness, and ignited. In order to in- 

 sure complete reduction of the bisulphates into the neutral 



