466 Intelligence and Miscellaneous Articles. 



tion of any trace of gas being expelled ; and the volume was read 

 off directly the retort had cooied to the temperature of the labora- 

 tory, thus preventing reabsorption. The hydrogen after all correc- 

 tions amounted to 46*4 cubic centim. 



Experiment IV. — In a fourth experiment, made like the last, 

 47*4 cubic centim. were obtained. 



AVe now have the following values for the volumes of hydrogen 

 expelled from the new sample of commercial zinc dust : — 



cubic centim. 



I. Soft glass retort, measured next day 31*2 



II. Hard glass retort, measured when cooled . . 36*8 



III. „ „ „ „ 46-4 



IV. „ „ „ „ . . 47-4 

 The volume in the last experiment is the largest I have been able 



to obtain, and shows that ordinary commercial zinc dust may 

 contain nearly fifty times its volume of hydrogen. 



Effect of Wetting on the Amount of Hydrogen Occluded. 



Experiment I. — I took the usual amount of zinc dust (6*4790 

 grammes) and thoroughly wetted it with boiling water. On drying 

 it in the water-oven until the weight was constant it was found to 

 have increased by 0*1924 gramme. The retort was then charged 

 with 6*4790 grammes of the dried dust, and heated in a retort 

 made from combustion-tubing. The air in the measuring-tube 

 before the experiment amounted to 3*9 cubic centim. The volume 

 of hydrogen evolved, after deducting the air and making all correc- 

 tions, amounted to 89*4 cubic centim., or 42 cubic centim. more 

 than in the highest result obtained from un wetted zinc dust. This 

 very large increase in the yield of hydrogen as compared with any 

 of the experiments made with the original zinc dust points very 

 clearly to the source whence it was obtained, and strongly tends to 

 confirm the view thrown out in my second paper, that this source 

 was water. It was again found in this experiment that it required 

 the highest heat of the lamp to drive off the last traces of hydro- 

 gen, and it was observed that during the operation a certain amount 

 of water was produced. On keeping the apparatus in the state in 

 which it was left after the experiment, it was found that the volume 

 of the gas and air in the measuring-tube became less day by day, 

 until, at the expiration of a fortnight, it only measured 80*4 cubic 

 centim. The absorption therefore amounted to 9 cubic centim. 

 As the air in the measuring-tube only amounted to 3*9 cubic cen- 

 tim., it became evident that the absorption was chiefly, if not 

 entirely, due to hydrogen. So that we have now conclusive proof 

 that zinc dust, in addition to taking up water and giving up its 

 hydrogen on heating, absorbs this gas at ordinary temperatures 

 when surrounded by it in a moist condition, thus confirming the 

 conclusion arrived at in my first paper from the phenomena ob- 

 served during the synthesis of trimethylamine. Whether it absorbs 

 the gas when it is in an anhydrous state I propose to determine 

 later on. 



Experiment II. — In a second experiment 6*4790 grammes of the 



