350 Chemical Contributions. 



through its bottom, and a test tube of a suitable size luted in with 

 clay. The phosphorus is put into the test tube ; the top of which 

 is loosely covered with a piece of broken crucible to prevent the 

 small pieces of quicklime from running down into it.* The lime is 

 then put in so as to fill this crucible and partly fill the upper smaller 

 one, which serves as a cover to it, and is luted on with some fine clay 

 a little moistened, (fig. 6.) The cover has also a small hole in its 

 top to afford an outlet for the air or volatilized phosphorus if there 

 should be any occasion for it. The whole is now placed upon the 

 grate of a furnace, with the test tube projecting through and appearing 

 below, and a charcoal fire kindled around it. The phosphorus may 

 be kept cool if it should be thought necessary, by making the tube 

 dip into the water, contained in a tin cup attached to the end of a 

 stick. When the crucibles and their contents are thoroughly red 

 hot, a chafing dish is substituted for the tin cup, and the phosphorus 

 rising in vapor produces the desired change. The phosphuret should 

 be preserved in a sealed vial. The same crucibles may be used a 

 number of times. 



The only purpose for which phosphuretted hydrogen is prepared 

 is for the exhibition of its property of spontaneous combustion. A 

 pleasing mode of exhibiting this is to immerse wholly the retort or 

 gas bottle in which it is generated in the water of the pneumatic cis- 

 tern. The gas rising at a distance from any object from which it may 

 be supposed to have been derived, and taking fire at the surface of 

 the water, presents a miniature representation of what the appearance 

 may have been when the Azores or Sandwich Islands were about to 

 emerge from the bottom of the ocean. 



It is the business of the chemist to ascertain the proper method of 

 preparing this gas ; its composition ; upon what its extreme combus- 

 tibility depends, etc. Will some one of the mathematical correspond- 

 ents of the Journal, investigate the nature of the forces exerted during 

 its combustion, and show how they result in the production of the 

 beautiful coronet which succeeds ; and why a rotatory motion around 

 the axis of the coronet is impressed upon the filaments of watery 

 vapor, and phosphoric acid of which it is composed ? 



* The crystalline limestones do not answer well for the preparation of the quicklime 

 that is to be used, there is nothing better for this purpose than a piece of chalk. 



