METUüD OF L)Ei'EKMIXrN(i MOLECULAR WEIGHTS. 3| 



indirect flmne, us sliown in the figure. In tlie case, liowever, of less 

 volatile R<ilvent:^, hucIi iva Avnter or even alcoliol, a piece of asbestos 

 car(l-])oar(l havins; a hole in the centre is n.ed instead, and the hoilino- 

 is produced hv direct flame. 



The height of tlie flame l)nth under tlie boiler and the b(.)iling 

 vessel has to be carefully regulated for each particula.r solvent a.ccord- 

 ing to its volatility ; and, in order to avoid tlie effect of any alteration 

 in the ga..^ pressure owing to constant openings and shuttings of gas 

 ta.ps in other parts of the lal^oratorv, the fjllowino- arrano-ement is 

 adopted and is found to answer admiral)ly. The gas tube is connected 

 witli tln-ee Ihuisen Inn-ners and, fully opening the gas tap, the burner 

 nearest tlie tap is liglited. This acts a,s a ga.s regulator. The supply 

 of gas to the other two Ijurners is adju, -ted by means of screw-clips 

 k and / ; a.iid, since the amount of gas supplied to the regulator- 

 burner is incompara.bly grea.ter than that supplied to the two others, 

 no effect of alterations of ga.s pressure in the mains can be perceived 

 in the latter. Thi.:! circum: taiice is of considerai>le importance, 

 because I am thereljy enaljled to use the budlj of the thermometer 

 always naked, there being no necessity to envelope it with asbestos 

 fibres, as when working vrith 15eckmann's apparatus. 



The therinometer which I use includes onlv a ranofe of 6°c. and 

 is graduated into jijyth. of a degree. Each of these divisions (about 

 0.1 mm.) can be readily esthnated into rVth by means of a reading 

 telescope, which I ahvays use, so tha.t the thermometer can indicate 

 T^V^th of ti degree. There is an arrangement in tlie instrument by 

 which the quantity of mercury in the bulb may be increased or 

 diminished, so that it can be used either for hnv or high temperatures. 

 '1 hi.^ instrument has alread}^ been described by Beckmann. 



The whole arrangement is exceedingly sim|)le, and can ])e set up 

 by any one with materials commonly found in :dl l:d)oratories. This, 



