342 Dr. L. Bleekrode. On the Determination of the 



with capillary tubes b and c ; this was transformed into a vessel 

 having two parallel side plates, and free from leakage even at high 

 pressures, in the following manner. 



The ends of the cylinder were both ground as flat as possible, on 

 each of them a thin circular disk pierced in the centre and cut from 

 lead or tin, according to the liquid examined, was put, subsequently 

 a plane glass plate that had been previously submitted to the 

 toughening process of La Bastide (in some cases a quartz disk was 

 used) followed, and lastly a perforated smooth leathern disk. The 

 whole was held together by two perforated steel plates forming the 

 ends (fig. 1 shows the construction, e and g showing the apertures) 

 and connected with another by three screws turned on as strongly as 

 possible.* A perfectly gas-tight vessel was thus obtained that did 

 not allow leakages even at pressures above a hundred atmospheres, as 

 was tried with the compression apparatus of Cailletet. And I must 

 point out here especially the property of toughened glass to resist in 

 the most effective way the always more or less unequal pressure, 

 exerted by the three connecting screws, when even quartz plates 

 being 3 millims. thick burst to pieces, if the screws happened to be 

 turned on nnequally. The glass plates, having only a thickness of 

 1 to 1*5 millims., were cut out of very plane surfaces, and after being 

 reduced to the proper 'dimensions, suffered the toughening operation, 

 that was applied with much care. Of course some of them got their 

 surface more or less impaired and rendered less transparent ; from a 

 great number the best ones were chosen, and they never became unfit 

 for use. 



In most cases the lead disks, procuring a very successful closing, 

 were not attacked in a chemical way by the liquefied substance if no 

 moisture accompanied it (with hydrobromic acid tin disks resisted 

 better), and thus commonly a perfectly clear liquid filled the 

 cylindrical vessel.f In how effective a way leakages were prevented 

 may be concluded from the fact that liquid carbonic acid was often 

 kept during more than a year in such hermetically closed vessels, and 

 even when heated during several hours above 30 C., without a 

 perceptible loss occurring. 



If the gas could be evolved chemically in a sufficient quantity to 

 become liquid by its own pressure exerted, the cylindrical vessel was 

 fixed with the blowpipe on a stout bent glass tube (fig. 2), having a 

 length generally of 40 centims., an inner diameter of 6 millims., an outer 

 diameter of 10 millims. The appropriate substances were put in the 



* The steel plates were 8 millims. thick ; in the figure only two screws could be 

 represented entirely. 



f Organic substances, applied to obtain a gas-tight closure, should be avoided 

 when working with apparatus for liquefied gas, as these are commonly absorbed by 

 the liquids, rendering them often opaque. 



