Professor Green on a case of sudden Crystalization. 93 



culty, and we let in both gases at once, or the hydrogen 

 only, and the oxigen as it is wanted, and thus produce as 

 much water as we choose, or as our gases will afford. 



The experiment may be performed without first fiUing 

 the bottle with oxigen gas, and by operating with it full of 

 common air, but the nitrogen, in a degree, obstructs the 

 combustion, and the result is less satisfactory. 



This little application of Mr. Hare's blowpipe may, per- 

 haps, be of some use to chemical demonstrations, and 

 serves to evince the additional value of this fine instrument. 



For an illustration of the above description, see the draw- 

 ing on a plate, at the end of this Number, where a section 

 of the pneumatic cistern, with the air cells — the recurved 

 tubes coming from them and terminating in the blowpipe, 

 and the connexion of the latter with the bottle, are ex- 

 hibited. 



Art. XIV. — On an instance of instantaneous Crystaliza- 

 tion— by Professor Green, of Princeton. 



The instantaneous crystalization of a saturated solution 

 of the sulphate of soda or common Glauber's salt, is fa- 

 mihar to every one who makes chemical experiments, and 

 perhaps the crystaline process I shall now mention, has been 

 often noticed before — I send you, however, the following 

 account, as I have not seen it any of the books on Chem- 

 istry. 



In preparing the nitric acid from nitrate of potash and 

 sulphuric acid, I had occasion to stop the process just as 

 the red fumes of the nitrous gas made their appearance, 

 and of course, when the nitrate of potash was completely 

 dissolved in the sulphuric acid- — the next day I found the 

 solution perfectly transparent, and upon admitting the at- 

 mospheric air no change took place, but upon dropping into 

 it a small piece of the nitrate of potash, crystalization im- 

 mediately ensued, and the whole was quickly solidified. 

 There was, I think, a larger quantity of caloric extricated 

 during the above process, than in the instantaneous crystali- 

 zation of the sulphate of Soda — another difference was, 

 ibat the solidification did not, as far as I observed, com- 



