Intelligence and Miscellaneous Af tides, ISl 



the carbonic acid to be 194) prepared by calcining the bicarbo-. 

 nate into a watch-glass of known weight, and left it exposed to the 

 atmospliere in a room in which no fire was kept. By frequently 

 weighing the glass and its contents 1 found the gain of weight to 

 be as follows : 



Oct. 21 



22 

 23 

 24 

 25 

 26 



Weight gained. 



3-3 grains. Oct. 



. 6 1 



. 91 

 ,. 11-8 



. 13'8 

 ,. 161 



The salt having concreted into a rather hard mass was now broken 

 up, so that it might the more readily acquire more moisture. 



Weight gained. Weight gained. 



Nov. 1 .... 31*6 grains. Nov. 3 .... 386 grains. 

 2 34-1 4 40-8 



The salt was now removed from the watch-glass, crushed and 

 spread over the surface of a dinner plate, so that the process might 

 be sooner finished. 



Weight gained. Weight gained. 



Nov. 6 .... .56*1 grains. Nov. 16 78*6 grains. 



11 .... 77-6 21 .... 78-6 



14 .... 78-6 



1 left it exposed to the atmosphere till the 4th December, when I 

 found it to be of the same weight as on the 21st November. It was 

 therefore evident that no more water could be absorbed. 



Now the 78*6 grains of water absorbed are only 1 '4 grain short 

 of being equivalent to ten atoms *, and it is probable that a waste 

 of that quantity of salt may have been made in the numerous weigh- 

 ings. If this be granted, the author says he is right in concluding 

 that the anhydrous carbonate acquires water until it is of the same 

 constitution as the crystallized carbonate, if exposed to such an 

 atmosphere as he made use of, one in which the temperature ranged 

 from 53° to 43°, and whose vapour point is not more than 7° below 

 the temperature nor less than 5°. The vapour point was ascertained 

 by the aid of an hygrometer on tiie principle of Leslie's, and de- 

 scribed by the author at the meeting of the British Association at 

 Edinburgh. 



On the 20th of October, 100 grains of crystals of carbonate of 

 soda were exposed in the same room as that above alluded to; by 

 one day's exposure 2^ grains were lost, and no further loss occurred 

 although the expo.sure was continued till the 4th of December. 

 Mr. Watson therefore concludes that the water was merely adherent, 

 and not combined. 



In a room in which a moderate fire was regularly kept Mr.Watson 

 exposed 20 grains each of crystals of sulphate of soda, of crystals of 



[* Onlv 04 gr. short of 10 atoms, if the usual equivalents are adopted, 

 47-4: 78-6: ;54 . 89-6.— Edit.] 



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