316 Scientific Intelligence. 



them moist before explosion occurs. Sharp solid fragments, such 

 as glass or sea sand were found to be without effect. But frag- 

 ments of platinum foil or wire made it impossible to bring about 

 an explosion even at 715°, silent union always taking place. 

 Carbon monoxide and oxygen, in suitable proportion to form car- 

 bon dioxide united silently in the apparatus, for the most part ; 

 the temperatui'es, when explosion did occur, varying from 636° 

 to 814°. Mixtures of oxygen with gaseous hydrocarbons, except- 

 ing perhaps marsh gas, afforded the most trustworthy explosion- 

 temperatures, since there was practically no silent combination. 

 Marsh gas and oxygen explode as a rule, at temperatures varying 

 from 656° to 678° ; though sometimes silent and complete combi- 

 nation took place. Ethane and oxygen detonated at 622°, 605° 

 and 622° respectively ; ethylene and oxygen at 577°, 590° and 

 577° in three consecutive experiments. Acetylene with oxygen 

 explodes with remarkable violence, at 510°, 515° and 509°. Pro- 

 pane with five volumes of oxygen, gave 548°, 545° and 548° as 

 the explosion-temperature in three experiments. Propylene, 

 with four and a half volumes of oxygen exploded at 497°, 511° 

 and 499°. Isobutane, with six and a half volumes of oxygen de- 

 tonated at 549°, 550° and 545° ; and isobutylene at 546"°, 548° 

 and 537°. Finally coal gas mixed with three volumes of oxygen, 

 was found in three remarkably concordant experiments, to ex- 

 plode at 649°, 647° aud 647°. A mixture of coal gas with air 

 could not be exploded however under these conditions of experi- 

 ment. It will be noticed that the temperature of explosion falls 

 as the content of carbon increases; the mean temperatures, for 

 example, for methane, ethane and propane being 667°, 616° and 

 547° respectively. Moreover the temperature falls also with the 

 degree of saturation, the less saturated the hydrocarbons, the 

 more readily do they ignite in contact with oxygen ; ethane, 

 ethylene and acetylene exploding at 516°, 580° and 511°; pro- 

 pane and propylene at 547° and 504° ; and isobutane and isobu- 

 tylene at 548° and 543°. As might be expected, these differences 

 arising from greater or less saturation diminish as the series is 

 ascended. — Ber. Berl. Chem. Ges., xxvi, 2421, November, 1893. 



G. F. B. 



4. On the Composition of Water by Volume. — By means of 

 improved apparatus, Scott has continued his investigation of the 

 proportion by volume in which hydrogen and oxygen unite. The 

 measurements were all made at constant volume, the pressure 

 only being varied. And as vaselin was found to introduce 

 traces of the oxides of carbon into the gases, syrupy phosphoric 

 acid was used lor lubrication. The oxygen was prepared from 

 silver oxide and the hydrogen from sodium and steam. In cer- 

 tain experiments the hydrogen was further purified by absorption 

 in palladium. In five series of 53 experiments the mean ratio of 

 hydrogen to oxygen was found to be 2-002435 ±0*00006, the im- 

 purity being supposed in both gases equally; or 2'002431 ± 

 U-00006, the impurity supposed in hydrogen alone. Rejecting six 



