of Asia Minor. 377 



r 



The examination of the silica attracted considerable attention, 

 from the fact that we are in the habit of always estimating it as 

 uncombined silica, even when found in alkaline waters. Although 

 my researches are sufficient to prove to my mind the inaccuracy 

 of thisj still I have not thought proper in this paper to deviate 

 from the rule generally adopted, leaving it to more extended re- 

 search to decide the point. 



In the analysis of the waters of Broosa, nearly all of which 

 are alkaline, the following fact has been observed; that on con- 

 centrating a considerable quantity of the water to a small bulk, 

 all the carbonate of lime is precipitated and a portion of the silica 

 (whether in combination with lime or not is not yet decided); 

 but a large portion of the same still remains in solution, as well as 

 some lime, although the water is alkaline with an excess of car- 

 bonate oi soda. The silica is in such quantity that it could re- 

 main only in solution in combination with an alkali, in fact there 

 IS a silicate of soda and lime present. 



The question here arises whether the silica was in a state of 

 combination before the water was concentrated, or is it a result 

 that has taken place during the evaporation ; this question can 

 only be decided by more extended investigation. 



The observation of the above fact has led me to adopt the fol- 

 lowing method of estimating the silica in mineral waters. Take 

 a certain quantity of the water, evaporate almost to dryness, add 

 hydrochloric acid, a little more than is required to saturate the car- 

 bonates present ; continue to evaporate to complete dryness, and 

 then add water acidulated with a little hydrochloric acid, filter 

 and wash the silica that remans on the filter; in this way we 

 are sure to have the silica perfectly free from any silicate. 

 . The method adopted for estimating the alkalies will be men- 

 tioned in a {q\v words, as more details of it will be given in a 

 paper devoted especially to that subject, the method has particu- 

 lar reference to the separation of the alkalies from magnesia. 



Take the solution filtered from the silica, evaporate to dryness 

 to drive off the excess of acid, add a Uttle water to redissolve, 

 then add pure lime water and filter, when the chlorids of th6 al- 

 kaline metals and calcium with excess of lime will pass through, 

 the magnesia, alumina, oxyd of iron, &c., remaining on the filter. 

 Separate the lime with carbonate of ammonia, or still better 

 ^^ith oxalate of ammonia, evaporate to dryness, and heat to 

 ^n^^e off the ammoniacal salts, when nothing but the chlorids of 

 alkaline metals will be left which can be separated in the ordi- 

 nary way. 



This completes the description of all the thermal waters of Asia 

 Mmor which have as yet come under my notice, with the obser- 

 vations that the investigation have given rise to. 



J 



^ 



