204 Miscellanies. 



A. M., Professor of Natural Science in the Wesleyan University, Mid- 

 dle town, Ct. — The remarks I have to make, have reference to the con- 

 ditions required in order to obtain the greatest quantity of liquid, and, 

 as a matter of course, of solid carbonic acid, from a given quantity of 

 materials. 



The different sets of apparatus for solidifying carbonic acid that have 

 been made in this country, with one or two exceptions only, it is believed, 

 have been constructed in every essential particular, precisely like that 

 of Dr. Mitchell,* who enjoys the honor of having been the first in 

 America to repeat the beautiful experiment of Thilorier. This appa- 

 ratus accomplishes the, object perfectly ; but the quantity of solid acid 

 obtained from it at a single charge, as it is ordinarily used, is probably 

 considerably less than the same materials are capable of affording, by 

 a little different management. 



In order to obtain the greatest quantity of the acid, in the liquid 

 form, from a given quantity of materials, it seems to be requisite that 

 three points be particularly attended to. First, the capacity of the re- 

 ceiver should sustain a proper I'atio to that of the generator ;t secondly, 

 the quantity of materials used should be sufficient very nearly to fill the 

 generator ; and thirdly, the difference of temperature between the re- 

 ceiver and generator, when the liquid acid is distilled over, should be 

 as gr^at as practicable. 



As it regards the first point, without presuming to speak positively on 

 the subject, my experience leads me to think the capacity of the re- 

 ceiver should be about one sixth of that of the generator ; certainly it 

 should not exceed one fifth. In the apparatus used in this institution,! 

 the receiver is but little nnore than one seventh of the capacity of the 

 generator, but at every operation, when the generator is properly 

 charged, it is completely filled with the liquid acid, and the probability 

 is that more might be obtained if it was a little larger. If however 

 the capacity were more than just sufficient to contain the acid in the 

 liquid form that distills over, all the additional space would of course 

 be filled with the same acid in the form of gas but exceedingly dense, 

 so as to cause an essential diminution in the quantity of liquid. In 



* Joui-nalof the Franklin Institute, Vol. xx, p. 289, and Vol. xxx, p. 346, of this 

 Journal. 



\ Dr. Mitchell gave the XiRvne, generator, to the vessel into which the bicarbo- 

 nafe of soda, sulphuric acid, &c. for forming the carbonic acid, are placed ; and 

 called that the receiver, into which the liquid acid is distilled; and his terms have 

 been universally adopted. 



t Described in Vol. xxxviii, p. 297, of this Journal. It is there stated tliat the 

 capacity of the receiver is about one pint, but it should have been three gills. 

 The mistake was made by attempting to ascertain its capacity by external meas- 

 urement, and calculating its solid inches. 



