OASOMETUIC ANALYSIS. 



OASOMETRIC ANALYSIS. 



figure. It ii more simple in its construction than the foregoing, but 

 leu certain in iU results, on account of the escape of gas which occurs 

 if it be not immersed sufficiently deeg in water or mercury : it is a 

 modification of an instrument invented by Dr. Priestley. The only 

 additional explanation required is, that A is a moveable metallic wire 

 with a knob at the end, which u raised near enough to the knob at the 

 top of the instrument to allow of the passage of the electrical spark. 



Dr. Ure also contrived a modification of Volta's eudiometer, which 

 renders the experiment easy of performance by a single person. This 

 instrument is shown by the figure. It con- 

 sists of a glass Kiphou, having on interior 

 diameter of from 2-10ths to 4-lOths of an 

 inch ; its legs are nearly of equal length, each 

 being from six to nine inches long. The 

 open extremity is slightly funnel-shaped ; the 

 other is hermetically sealed, and has two 

 platinum wires inserted : the legs are about 

 one-fourth to one-half an inch asunder. The 

 instrument having been graduated, it is to be 

 filled with water or mercury, and the gas 

 transferred into it in the ordinary manner ; 

 then being upright, part of the fluid in 

 the open leg is displaced by inserting a glass rod, or in some other 

 manner. The open leg ought to contain at least two in. 

 air between the thumb and the mercury : this atmospheric column 

 serves as a recoil-spring, enabling the operator to explode considerable 

 quantities uf gas without inconvenience or danger. The open leg 

 being grasped by the baud, the thumb is to be placed lightly over the 

 aperture, so as to close it, and at the same time to touch one of the 

 wires; a spark taken from the conductor to the other wire passes 

 through the gas, inflaming it, and is conducted off by the thumb and 

 hand. The gas in expanding depresses the fluid beneath it, whilst, as 

 already noticed, the air ill the part inclosed by the thumb acts as a 

 spring to restrain the violence of the explosion. If a charge from a jar 

 is to be passed, then the thumb must not be allowed to touch the wire 

 whilst closing the aperture. When the jar is charged, the wire con- 

 nected with the outer coating is first to be hooked upon the euii 

 wire nearest the thumb, and securely retained there, so as not to slip 

 during the experiment ; and then the knob of the jar is to be brought 

 to the other wire and the gas inflamed. 



After explosion, when the condensation of volume ensues, the thumb 

 will feel pressed down to the orifice by the superincumbent atmos- 

 phere. On gradually sliding the finger to one side and admitting the 

 air, the mercurial column in the sealed leg will rise more or less above 

 that in the other ; mercury is then to be poured in till the equilibrium 

 is restored, and the resulting volume of gas is then read off. 



Dr. Ure states that with the above instrument he has exploded half 

 a cubic inch of hydrogen mixed with a quarter of a cubic inch of 

 oxygen, as also a bulk nearly equal of an olefiant gas explosive mixture, 

 without any unpleasant concussion or noise. 



Dobereiner suggested a eudiometrical process, founded on his curious 

 discovery of the property which spongy platinum possesses of causing 

 the combination of oxygen and hydrogen gases. In this eudiometer 

 the combination occurs without explosion, and yields results of con- 

 siderable accuracy. Dobereiner found that when the spongy ]>1 

 was mixed with certain substances, so as to prevent its immediate and 

 explosive action, it caused the oxygen and hydrogen to combine with 

 moderate rapidity. The Lite Dr. Henry, who performed a most 

 important and accurate scries of experiments on this eudiometrical 

 process, recommended a mixture of three parts of spongy platinum 

 and two of fine china clay made into a paste with water and moulded 

 into spherules about the size of a pea; these were fastened to a 

 platinum wire, that they might be removed after the action was over. 

 They should be heated and suffered to cool a short time before use : 

 they suffer no loss of power, and possess the great advantage over the 

 electric upark, that they act upon gaseous mixtures which contain so 

 little oxygen and hydrogen that they cannot be fired. The late Dr. 

 Turner ascertained that it was possible to determine the presence 

 of jfo of hydrogen or oxygen in a gaseous mixture ; whereas, when 

 these gases formed -fa of a mixture, they could not be detected by 

 electricity. The effect takes place more rapidly in large than in small 

 tubes. 



There are various gases which imjicdc the action of the platinum 

 ball*. It appears from the experiments of Dr. Henry, that when the 

 compound combustible gases, inixtil with cadi other, with hydrogen, 

 and with oxygen, are exposed to the Iwills of platinum, the several 

 gases are not acted upon with equal facility ; that next to hydrogen 

 carbonic oxide is most disposed to unite with oxygen, then olefiant gas, 

 and lastly, light carburetted hydrogen. 



Dr. Henry observed, that the property inherent in certain gases of 

 retarding the action of platinum, when they are added to explosive 

 mixtures of oxygen and hydrogen, is most remarkable in those which 

 posses* the strongest attraction for oxygen. Heat occasions the 

 platinum balls to act in many cases in v which no combination would 

 occur without it, 



The instrument* and methods above described were not only almost 

 exclusively limited to the determination of the oxygen in atmospheric 

 air, but they wws also both imptrfMt and incorrect, and th analysis 



of gaseous bodies cannot be said to have become organised into any- 

 thing like a system until Professor Bunsen applied himself to its 

 improvement, which he effected lev by the use of new instruments 

 than by the perfection of the old ones, and the correction of the 

 numerous sources of error which rendered the result* of earlier < 

 menters so little trustworthy. To this accomplished chemist, to 

 Regnault and others, this branch of chemical analysis owes its present 

 state of perfection, which is rarely equalled and never surpassed in 

 other de)rttiH nts of analytical chemistry. 



Ingenious instruments for the analysis of gases hare been contrived 

 by Messrs. Regnault and Reiset (see ' Annales de Chiruie et de physique,' 

 t. xxvi., p. 333) and by Dm. Williamson and Russell (' Philosophical 

 Magazine,' vol. xvi., p. ;V_'n Imt in this article we shall confine our- 

 selves to the description and use of an apparatus invented by Messrs. 

 Frankland and Ward, which may be employed in all the operations of 

 gaseous analysis, and which is represented in the annexed figure. A is 

 a tripod base furnished with levelling screws and carrying the vertical 

 pillar mi which supports on one side the moveable gutta 

 mercury trough c, with rack and pinion a a, and on the other the glass 

 cylinder DD with its contents. This cy Under is 36 inches long and 4 

 internal diameter ; its lower extremity is cemented into an iron 

 ring c, the under surface of which permits of being screwed 

 tight upon the iron platform </ by the intervention of a caoutchouc 

 ring. The circular platform il is pierced by three tubes which 

 terminate below in the T piece i: E. Into these tubes ore screwed the 

 steel caps tee which receive the open extremities of the glass 

 tubes F, u, H. The T piece E E is furnished with a three-way cock /, 



and with a hiniple cock ;/, by means of which the tubes in D 11 > 

 connected either with each other or with the exit nozzle h. Of th<> 

 glass tubes FOB, one F is only slightly shorter than the containing 

 cylinder, another u is 3 or 4 inches longer, whilst a rises at least 6 

 inches higher than the latter. F and B are each about 15 millii 

 diameter ; o is somewhat wider and open at top. 11 has a millimeter 

 scale etched upon it, and its upper .extremity terminates in a small 

 funnel i, the throat of which can be cloud by a ground (topper. The 



