at the Royal Institution, 1908-1916 755 



*' If liquid oxygen is absorbed in wood charcoal or cotton wool and a 

 part of the body heated to redness, combustion can start with 

 explosive violence." Liquid air has been extensively used of late 

 years in conjunction with charcoal as an explosive mixture in blasting 

 operations and there is little doubt that this most simple of all 

 blasting agents may play an important part in such operations in 

 future. 



In this discourse, much was said of the cooling effect produced 

 on discharging gases through fine apertures and of the use of coohng 

 coils. This was preliminary to a demonstration of the liquefaction 

 of hydrogen and its appearance in the form of a jet. With the 

 appliances then available, it was not posssible to collect the liquid in 

 quantity. When the liquid jet was allowed to impinge upon liquid 

 air or oxygen, these were transformed into hard white solids. 



It had long been evident that even Cailletet had not succeeded in 

 liquefying hydrogen. This was first effected by Wroblewski in 1898 

 but neither he nor Olzewski was able to deal with it in a tangible 

 form. It was first collected as a liquid at the Royal Institution 

 laboratory on May 10, 1898. At the commemoration of the Centenary 

 of the Royal Institution on June 9, 1898, Prof. Dewar was able to 

 exhibit no less than a litre of the liquid on the lecture table. Since 

 then it has been nearly as familiar to us as liquid air and we have 

 witnessed the most astonishing demonstrations of its cooling capacity. 



Miss Agnes Gierke has given an account of the work in her Essay 

 in this series. 



A return was made to the " Properties of Liquid Oxygen " in the 

 Friday evening lecture on January 22, 1897. The absorption spectra 

 of gaseous and liquid oxygen and of liquid air were then considered 

 — a subject of interest to all spectroscopic inquirers who observe 

 through our atmosphere. The results of an inquiry carried out in 

 conjunction with Prof. Fleming into the numerical values of the 

 magnetic permeability and susceptibility of liquid oxygen were then 

 brought forward and demonstrated. 



The next Friday evening (April 1, 1898) was devoted to " Liquid 

 Air as an Analytical Agent." A most daring demonstration was given 

 on this occasion by pouring liquid air from a tin can — filled by dipping 

 this into a 5-gallon jar full of the liquid — into a large red-hot silver 

 basin ; the liquid remained as quiescent at this high temperature as 

 in cooler vessels and maintained a spheroidal condition — that is to 

 say, it was suspended over an atmosphere of gas produced at the 

 heated surface. 



The apparatus shown in the figure on p. 816 of Vol. XY. of the 

 Institution Proceedings was then explained and shown in action. 

 The apparatus had been exhibited and the results obtained with it 



3 J) 2 



