Chein icu I Con iributions. 



345 



Art. XL — On a Substitute for J'Velihei-'s Tube of Safety, withJVo- 

 tices of other subjects; by E. Mitchell, Professor of Chemistry, 

 Mineralogy, &ic. University of North Carolina, 



Welther's tube of safety, including under this title the three- 

 branched tube, with an uniform bore, as well as that furnished with a 

 bulb, is a convenient piece of apparatus in many operations, but is 

 not without its defects. 1. The three parallel branches make the 

 upper part too heavy for the slender stem that is to support it. 



2. From its form it cannot be attached to the apparatus with which 

 it is to be connected, without considerable danger of fracture. 



3. When the fluid is once set a running through it, the lower part 

 sometimes acts as a syphon, and carries over more of the acid or 

 otlier substance we are introducing, than was intended. 4. Unless 

 the upper leg be made most inconveniently long, its insulating power 

 is feeble. 5. For its size and simplicity it is a costly article. 



The remoteness of my situation from glass-houses and other man- 

 ufacturing establishments, makes it quite impossible for me to get 

 any thing, that may have failed in the course of my experiments, re- 

 placed within a moderate time ; and it is therefore important for me 

 to contrive such modifications of apparatus, as shall render me less 

 dependent on distant artists. On an emergency of this kind, I fell 

 upon the following substitute for Welther's tube of safety, which I 

 propose to such of the chemists, as may be placed in circumstan- 

 ces similar to my own. It has this at least to recommend it, that 

 it requires only the beak of a broken retort, a few inches of 

 straight tube, a little emery, and such other articles, as are found in 

 every laboratory, for its construction ; and in regard to convenience, 

 I have found it so much superior, in many cases, to Welther's tube, 

 that I should retain it in any situation. The mode of constructing it, 

 will perhaps be best understood, from an account of the method of 

 fitting up a two-necked bottle, for making hydrogen, nitric oxide, 

 carbonic acid, and sulphuretted hydrogen gases. 



~h S 3 



Vol. XVII.— No. 2. 



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