Chemical Science, 475 



very fine fulgorites h<ive been shown in Paris and London * by 

 Dr. Fiedler, procured from Westplialia. Some of them, which, 

 althoui^h not put together, have been exhibited in fragments and 

 in drawings, were 19 feet long. These tubes consist of sand vitri- 

 fied on the internal surface, and rough on the exterior; they are 

 formed by the passage of lightning through a sandy stratum j and 

 although this has been well determined, yet M. Hachette thought 

 it might be well to add, to the knowledge already obtained, some 

 experimental proofs of the effect of powerful electric discharges 

 through powders of a convenient degree of fusibility. 



The most powerful battery in Paris was employed, and the elec- 

 tricity accumulated in it discharged through powdered glass pressed 

 into a hole made in a brick ; tubes exactly similar to fulgorites were 

 obtained, except that they were small and proportionate to the size 

 of the electrical apparatus used. One was 25 millimetres (0.984 

 inches) long, the external diameter, diminishing irregularly from 

 one end to the other, was from 0.118 to 0.059 of an inch, and its 

 internal diameter 0.0197. In another experiment, made with glass 

 and common salt mingled together, a regular tube 1 . 18 inch long 

 was obtained, externally 0.157 of an inch wide, and internally of 

 half that width. 



Experiments made with powdered quartz and felspar did not 

 succeed. The tubes, obtained as above, exactly resembled those 

 formed naturally, in the brownness of the internal surface, but 

 were very far short of them in solidity and strength, — a difference 

 to be anticipated from the nature of the agents used. — Annales de 

 Chimiey xxxvii. 319. 



4. Preparation of Hydr iodic Acid Gas. — ^The following process is by 

 M. Felix d'Arcet. Hypophosphoric (hydro-phosphorous?) acid is to 

 be evaporated until upon the point of evolving phosphuretted hy- 

 drogen gas, when it contains no more water than is essential to its 

 composition. It is then to be put into a small tube closed at one 

 extremity, and itsweight of iodine added j on applying a gentle heat, 

 hydriodic acid gas is liberated, and continues to be evolved for a 

 long time. The gas is perfectly pure, being free from excess of 

 iodine 5 it may be collected over mercury without the formation 

 of any iodide of mercury, or by letting the conducting tube de- 

 scend to the bottom of the collecting jar in the ordinary manner 

 for heavy gases. 90 or 100 grains of the acid gave as much as 1 20 

 cubic inches of hydriodic gas, pure and entirely absorbable by water. 



The residue of the operation is a mixture of phosphoric acid, 

 and the compound of hydriodic acid and phosphuretted hydrogen. 

 —-Annales de Chimiey xxxvii. 220. 



5. Test for Nitric Acid and its combinations. — Runge. — Pour a so- 

 lution of protomuriate of iron upon the surface of an amalgam of 



* See Proceedings of the Royal Institution, p. 434 of this Number. 



