on the Analysis of the Carbonates. 355 



cess, which occupies from fifteen to twenty minutes, drawing 

 through the apparatus fifty cubic inches of dry air, the bottle is 

 several times gently shaken from side to side, to promote the es- 

 cape of the combined carbonic acid from the liquid. The instru- 

 ment is now withdrawn from the appendages, and again placed 

 on the scale to be weighed. In this second weighing, it will 

 sometimes happen, that the apparatus loses while on the scale, a 

 small amount of * weight, rarely however exceeding a few thou- 

 sandths of a grain, arising as we have clearly proved, from the 

 gradual escape of more of the combined carbonic acid from the 

 liquid. In such cases we repeat the process of aspiration, after 

 which the weight remains without sensible diminution during 

 the weighing. 



In using the pipette form of apparatus, for the deliquescent car- 

 bonates, the substance to be examined is placed in a thin glass 

 tube, previously weighed. The tube is then drawn out nearly to 

 a point by the use of a weighed fragment of a glass rod over an 

 alcohol lamp. Sufficient heat being applied thoroughly to dry 

 the carbonate, the fine end of the tube is closed, and the whole 

 suffered to cool down to the surrounding temperature. The point 

 of the tube is then removed with a sharp file, to allow air to en- 

 ter, after which it is closed by the application of a small stopper 

 of wax cement of known weight. In this condition the tube, to- 

 gether with the little piece removed from its point, and the frag- 

 ment of rod, are placed in the scale and counterpoised. The en- 

 tire weight, thus obtained, diminished by the sum of the weights 

 of the tube, rod and stopper, gives the weight of the dry carbo- 

 nate in the tube. 



The pipette being charged with acid and adjusted so as not to 

 produce drops, the tube is allowed to fall into the bottle with such 

 force as to be broken, and the cork is instantly secured in its 

 place. To inject the acid into the bottle, we attach the large 

 drying tube to the upper drying tube of the instrument, and then 

 operate either by suction with the mouth applied to a little mouth- 

 piece at the other end of the apparatus, or by connecting it with 

 the appendage for aspiration. In all the other steps the process 

 is the same as where the bucket is employed. 



The weight of the carbonic acid employed, being then accu- 

 rately determined, the process has reached the stage at which it 

 has heretofore been regarded as terminated, but numerous obser- 



