204 



THE SOUTHERN PLANTER. 



weights put into the other scale. The acid is 

 then poured upon the marl, and, after all the 

 carbonic acid has been discharged, the equili- 

 brium is restored by adding weights to one, or 

 abstracting them from the other scale. In prin- 

 ciple, this method is entirely free from objection, 

 but as usually conducted, it cannot be relied 

 upon as accurate. This want, of precision 

 arises in the, first place from the escape of 

 aqueous vapor, along with the carbonic acid 

 which is discharged, thus making a greater 

 weight necessary for restoring the equilibrium 

 than is due to the quantity of carbonic acid 

 which has escaped — and secondly, from the 

 greater weight of the vessels containing the 

 marl and acid impairing the sensibility of the 

 balance, and thus rendering it impossible to es- 

 timate the carbonic acid to small fractions of a 

 grain. The first of these objections has long 

 been obviated in the chemical analysis of the 

 carbonates, by causing the gas as it escapes to 

 pass through a tube containing dried muriate of 

 lime ; and the latter has been in some measure 

 removed by a contrivance of the great practical 

 chemist, Rose ; which, however, as it is incon- 

 venient and uncertain in the manipulation, I 

 shall not here describe. 



The apparatus which I have devised is, I 

 Hhink, free from these objections, and enables the 

 operator to proceed with great accuracy and 

 despatch. It has the advantage of being very 

 easily constructed, and of being used with a 

 balance that can be procured at a very moderate 

 price. Moreover, the quantity of marl which 

 is necessary for experiment in no case exceeding 

 ten grains, specimens for analysis may very 

 easily be forwarded by letter. 



The balance which I use with this apparatus 

 is a small goldsmith's balance, such as may be 

 procured for a few dollars in New York. It is 

 very light, and turns, when unloaded, with the 

 one-hundredth of a grain. My set of weights, 

 obtained from Millington, in Philadelphia, ex- 

 tends to tenths and hundredths of the grain. 



The accompanying figure will convey a dis- 

 tinct idea of the apparatus and mode of using 

 it. One of the scales is removed, to admit of 

 suspending the apparatus by a double thread 

 over the hook of the beam. The other is made 

 of something light, as a piece of card. In this 

 way all unnecessary weight upon the beam is 

 avoided, and its sensibility preserved. 



A, is a light bulb of glass, blown very thin, 

 from a common piece of tube, and about one 

 inch in diameter. A cork is fitted to its mouth, 

 and through this the tapered ends of the bent 

 glass tubes, B and C, are passed air tight; the 

 extremity of the latter extending some distance 

 into the vessel. The tube B, through which 

 the gas escapes, is filled with fragments of mu- 

 riate of lime. The tube C, which contains the 

 muriatic acid, is furnished with a light piston of 



cork or cotton, in the centre of which is fixed a 

 rod or handle, made of a small stiff straw. — 

 This instrument, when charged with marl and 

 acid, does not weigh more than 120 grains. — 

 The whole load of the beam is, therefore, 240 

 grains, and it is still sensible to the one-hun- 

 dreth of a grain. 



The mode of proceeding with the analysis is 

 as follows : — Five or ten grains of the finely 

 powdered marl is introduced into the vessel A, 

 and then two or three drops of water added, to 

 assist the diffusion of the acid. The small end 

 of the tube C, now removed from the cork, is 

 dipped into some muriatic acid in a wine glass, 

 and the piston moved backwards and forwards 

 until the necessary quantity of acid has been 

 drawn in. The tube is then replaced in the 

 cork, and in this state the instrument is coun- 

 terpoised by weights in the opposite scale. The 

 piston being then gradually forced in, the acid 

 is injected drop by drop upon the marl, and the 

 gas escapes by the tube B, depositing the aque- 

 ous vapor in its passage on the muriate of lime. 

 Allowing the apparatus to rest until the gas has 

 entirely escaped, and the decomposition is com- 

 plete, the equilibrium is restored by placing 

 weights upon the clear top of the cork, or by 

 removing weights from the scale. In this way 

 the weight of the disengaged gas is accurately 

 determined, and the proportion of carbonate of 

 lime thence computed. 



An analysis of a specimen of marl from James 

 City, just completed, will serve as an illustra- 

 tion of the method. Ten grains of the finely 

 powdered marl were introduced with a little wa- 

 ter into the vessel A ; the instrument was then 

 charged and equipoised. The acid being in- 

 jected, the whole was allowed to rest for an hour. 

 The weight lost was 2.91 grains. Increasing 

 this in the ratio of 44 to 100, gives 6.61 grains 

 of carbonate of lime in the 10 grains of marl — 

 or almost precisely 66 per cent. 



The frequent calls upon me for the analysis 

 of specimens of marl, first led me to the con- 

 struction of this apparatus, and I have since 

 found it so convenient and accurate, that I can 

 recommend its adoption to such of your readers 

 as may have a taste for chemical inquiries con- 

 nected with agriculture. Any ordinary worker 

 in glass will construct the instrument, and skill 

 in manipulating with it may be soon and easily 

 acquired. Wm. B. Rogers. 



The farmers who are using marl will be 

 greatly indebted to Professor Rogers for the 

 convenient and cheap little apparatus above de- 

 scribed — which, judging from his description, 

 not only furnishes the cheapest and most con- 

 venient, but. likewise the most accurate mode of 

 analysing calcareous manures. It may be easily 

 constructed by any worker in glass — so easily, 

 indeed, that Mr. Rogers made his own by the 



sin?. 



