346 Professors W. B. and R. E. Rogers 



to the diminution =1 T \ inches; or for the sexagesimal second, 

 =0-000077 mile =4 T y T inches. 



These minute quantities are insufficient to account for the ge- 

 ological evidences of the diminished diameter of the globe, in- 

 ferred from facts stated in the work alluded to, unless the period 

 of time be regarded as almost infinite, but it is believed that a 

 clue is perceived, by which compensating forces would maintain 

 the time of rotation nearly uniform, and the day of nearly an 

 invariable length, even if the earth be either gradually or par- 

 oxysmally undergoing a slight change in its dimensions. 



Ohio University, Athens, Dec. 9lh, 1843. 



Art. XVIII. — An Account of some neio Instruments and Pro- 

 cesses for the Analysis of the Carbonates ; by Profs. William 

 B. Rogers and Robert E. Rogers, of the Univ. of Virginia. 



The importance of some ready means of determining the com- 

 position of the calcareous and other carbonates, so extensively 

 used in- agriculture and the chemical arts, and the frequent neces- 

 sity of such analyses in the course of chemical research, have 

 suggested various forms of apparatus and modes of proceeding 

 adapted to this purpose. Of these the most generally used are — 

 first, that of Rose, as described in his Chemical Analysis, in which 

 the quantity of carbonate present is determined from the weight 

 of the carbonic acid expelled ; secondly, that of mingling the 

 carbonate and hydrochloric acid in a graduated tube over mer- 

 cury, and estimating the amount of the pure carbonate from the 

 volume of carbonic acid which collects in the tube ; and thirdly, 

 that of adding to the carbonate an acid of known strength, until 

 neutralization is effected, and computing the amount of carbonate 

 from the quantity of acid used. To these may be added, the 

 modifications of Rose's apparatus employed by Fritche, and by 

 Erdman and Marchand ; the very neat process of Dr. J. L. Smith, 

 described in this Journal, Vol. xlv, p. 262, which is an application 

 of the last of the three methods above mentioned ; and the inge- 

 nious but cumbrous, and we think inexact, instrument recently 

 proposed by Drs. Will and Fresenius.* 



* We may also add the method recently proposed by M. Schaftgoetsch, (Poggen- 

 dorff, Ann. der Phys. und Chem. 1842,) which is as follows. In a platina crucible 

 holding about IS grammes of water, are placed from 2 to 7 grammes of glass of 



