100 HEINRICH ROSE ON THE COMBINATIONS OF 



with other precipitates, which are to be heated, taken out of the 

 filter ; the crucible was then closely covered with the lid, and ex- 

 posed for a long time to a moderate heat, which was gradually 

 raised to redness. This was continued until all the muriate of am- 

 monia had evaporated. The crucible was then left to cool, the lid 

 taken partly off, and the coal of the paper reduced in the usual 

 way to perfect ash. If this precaution is not taken, and if the salt 

 is heated too much at first, some undecomposed salt and metalUc 

 platina may be mechanically carried away with the vapours of 

 the muriate of ammonia. From the weight of the metalhc platina 

 the ammonia in the salt is deduced. The deteniiination of the 

 ammonia may be effected in this way with great accuracy, much 

 more so indeed than that of the carbonic acid. 



The determination of the carbonic acid may be effected by 

 two methods. The most accurate is to convert it into carbonate 

 of barytes, and to determine from the weight of this salt that of 

 the carbonic acid. The carbonate of ammonia was dissolved in 

 cold water in a bottle, which could be closed air-tight, and a so- 

 lution of chloride of barium was added to it ; if the combination 

 under examination does not consist of the neutral carbonate of am- 

 monia, some pure liquid ammonia is added, after which the flask 

 is closed, and left to stand at least for twelve hours, or longer. 

 Care must be taken not to use too little Mater for the solution, 

 and especially to test the ammoniacal fluid by a solution of the 

 chloride of barium, to see whether it is free from carbonic acid. 

 I have usually distilled the ammonia previous to the experiment 

 over quick lime. The liquid, after the twelve hours' repose, was 

 then passed through a filter, during which communication with 

 the air was avoided as much as possible, and boiling water being 

 poured upon the carbonate of barytes, it was filtered with the 

 exclusion of air. This was frequently, and for a long time, washed 

 Avith boiling water, but not until the water that passed through 

 was no longer rendered milky by sulphuric acid, the residue not 

 being quite insoluble in water. Repeated trials can alone deter- 

 mine when it is time to leave off the washing. The carbonate of 

 barytes must not be filtered for some hours after precipitation, 

 and until it has entirely settled. If it be filtered sooner, carbonate 

 of barytes is dep(>sited from the clear filtered liquid, even when 

 no communication with the air has taken place. 



When diy, the carbonate of barytes is heated. There is no 

 need to fear, that by burning the filter any of the carbonic acid 



