on the Analysis of the Carbonates. 347 



The instruments and processes which we are about to describe, 

 are the suggestions of a long course of experience in the labora- 

 tory — have been submitted to numerous and varied trials, and 

 have been carefully compared with the modes in general use ; so 

 that we feel some confidence in offering them, through the pages 

 of this Journal, to the criticism of practical chemists. 



I. Apparatus and process for the approximate analysis of the 

 carbonates. 



The apparatus first to be noticed is a modification of that de- 

 scribed by one of us (W. B. R.) in the Journal many years ago.* 

 Even in its early and ruder form, this instrument was found to 

 furnish useful approximate results, with so much more ease and 

 expedition than the methods commonly employed, that of Rose 

 included, as to prove of great value in the numerous economical 

 analyses of calcareous marls and other materials in which we 

 were then engaging. In its improved shape, combining greatly 

 superior accuracy with increased facility of manipulation, we 

 have used it very satisfactorily for the last eight years, in many 

 hundred of the ordinary analyses connected with the geological 

 surveys of Virginia, Pennsylvania and New Jersey. 



The instrument, as thus modified, is represented in fig. 1. It 

 consists of a light flask or bottle, measuring about two cubic in- 

 ches, a globular pipette drawn out to a very slender tapering tube 

 below, a gum-elastic bag secured air-tight to the top of the pi- 

 pette, and a drying tube, filled for the middle two thirds of its 

 length with chloride of calcium, and near the ends with loosely 

 packed cotton. The pipette and drying tube are passed through 

 a smoothly drilled cork, so as to fit air-tight, the former project- 

 ing three fourths of an inch into the flask. The cork is so ad- 

 justed as to be withdrawn along with the pipette, and the pipette 

 is charged without, separating it from the cork. This gives room 

 for the introduction of the carbonate into the flask, and obviates 

 the danger, after the pipette has been charged with acid, of touch- 

 ing its moistened beak to the cork. Lastly, the surfaces of the 



borax, which is fused by a double current spirit lamp. When cold — it should be 

 cooled under a desiccator, over sulphuric acid — it is weighed, and a weighed quan- 

 tity of the carbonate placed in it; the whole is now again submitted to fusion. 

 When again cooled as before, the loss of weight is carbonic acid. If the substance 

 contains water, it is driven off at the same time with the carbonic acid, and of 

 course its quantity must be estimated in the usual way. — B. S. Jr. 

 * Vide Am. Jour. Vol. xxvn, p. 299. 



