312 Scientific Notices — Miiieralogy, [Oct. 



2. Spontaneous Combustion of Chlorine and Olefiant Gas, 



It has long been known that chlorine and hydrogen in mixture 

 are liable to explode, when struck by the direct rays of the sun, 

 and an instance is related in the American Journal, (vol. iii. p. 34 1 ,) 

 in which these two gases exploded, even in the diffuse light of 

 a cloudy and snowy day. I have not met with any account of 

 a similar action on the part of chlorine and olefiant or heavy 

 carburetted hydrogen. It is well known that when mingled, in 

 about equal volumes, they combine quietly, and become con- 

 > densed into the pecuhar aromatic, oily-looking substance, since 

 called chloric ether. This effect I had so often witnessed, and 

 had never seen any material variation in the result, that 1 was 

 not prepared to look for any thing else. But in an experiment 

 of this kind, (January 5, 1826,) happening to mingle the chlo- 

 rine with the olefiant gas in such a manner, that the latter gas 

 was uppermost, the combination went on more slowly than when 

 the reverse order was observed ; and the oily matter was gra- 

 dually precipitated, but was less abundant in quantity than 

 usual. Repeating the experiment, in the same manner, the 

 gases had remained in contact a few minutes, apparently with- 

 out mingling much except at their surfaces — the chlorine pre- 

 serving its peculiar colour and the other gas its colourless trans- 

 parency, when, suddenly, a bright flash pervaded the bell-glass, 

 which was of the capacity of five or six quarts ; it was raised 

 out of the water with a slight report — a dense deposit of char- 

 coal lined the glass and floated on the water of the cistern, and 

 the chlorine disappeared. The appearances were much like 

 those which are exhibited when a rag dipped in oil of turpen- 

 tine is placed in ajar of chlorine gas. 



Reflecting on the circumstances, I was led to believe that the 

 peculiar effect, in this case, arose from the fact, that, owing to 

 the great difference in the specific gravity of the two gases, the 

 action took place principally at the two surfaces of contact, and 

 thus the chlorine acting upon a comparatively thin stratum of 

 inflammable gas, the two became so heated, as to pass into vivid 

 combustion. Every new occurrence in practical chemistry, 

 which may involve danger, ought to be exactly stated, that we 

 may be aware of contingencies not otherwise anticipated. — 

 (American Journal of Science.) 



Mineralogy. 

 3. Thenardite, 



This substance was discovered in the Salt Works of Esper- 

 tines, about five leagues from Madrid, by M. Rodas, a Spanish 

 manufacturer. The crystalline form is described by M. Cordier, 



d the analysis is by M, Casaseca, Professor of Chemistry at 



