A MODIFIED HALDANE GAS ANALYZER FOR ANALYSIS OF MIXTURES WITH ONE HUNDRED PER CENT ABSORBABLE GAS

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1 A MODIFIED HALDANE GAS ANALYZER FOR ANALYSIS OF MIXTURES WITH ONE HUNDRED PER CENT ABSORBABLE GAS BY H. C. BAZETT (From the Department of Physiology, University of Pennsylvania, Philadelphia, and the Department of Medical Research, University of Toronto, Toronto, Canada) (Received for publication, January 27, 1941) Some years ago a need arose for a gas analyzer that would allow the concentrations of acetylene and oxygen to be raised above those which can be handled in the ordinary type of machine. The present analyzer was designed for this purpose. In determinations of cardiac output by the Grollman method, the presence of higher concentrations of either acetylene or oxygen or of both was not found to affect the estimate significantly. The special analyzer was not therefore described. With the recent intensified importance of the desaturation of the body with nitrogen before flying at great heights, the determination of the rate of nitrogen elimination from the body attains greater importance. For such determinations, as well as for the exact estimation of alveolar air concentrations in individuals breathing high concentrations of oxygen, the apparatus here described has a special usefulness. For this reason a description is now submitted. The apparatus is so designed that it can be utilized for many types of analysis. For the analysis of expired air an accuracy can be attained that is several times greater than that obtainable with the ordinary Haldane analyzer. Apparatus-The principles involved are throughout those developed by Haldane. The main burette in which the gas being analyzed is contained is, however, double; the two parts of which it is composed are connected by a T-stop-cock. The larger of 1 Bazett, H. C., Scott, J. C., Maxfield, M. E., and Blithe, M. D., Am. J. Physiol., 116, 551 (1936). 81

2 3 R2 FIG. 1. The two parts of the double burette (1) and (2) are shown diagrammatically within their water bath F. The numbers on the tubes indicate the graduated sections (graduated in 0.01 ml.) with zero positions at C and D respectively. Burette (1) is made of tubing of 3.5 mm. bore and (.2) of tubing of 3.2 mm. bore. The upper tubing connecting to the cocks A and B as well as that connecting to the absorbers is of 1.5 mm. bore. Between (1) and (2) lies the control burette (S) consisting of tubing of 5 to 6 mm. bore. All three burettes are connected below with their reservoirs Rl, Rd, and RS by rubber tubing with cocks intervening. On the tubing connecting to burettes (I) and (3) are screw clamps G to effect fine adjustments. Cock E connects the control system to the room when required. Cocks H and J connect to the CO2 absorber Z and the oxygen absorber K. They may be of the T-type as shown or may have double oblique bores. Tube L beyond cock J serves for cleaning or for connecting a third absorber. Rubber tubing connections are shown by shading. FIG. 2. Various combinations of the positions of cocks A and B are indicated. 82

3 H. C. Baaett these two burettes (labeled (1) in Fig. 1) contains 16 ml., 12 ml. in the bulb and 4 ml. in the graduated tube below it. It alone is used to pump the gas back and forth. The smaller (labeled (2) in Fig. 1) consists of three bulbs each of 3.5 ml. with a graduated section of tube of 0.5 ml. capacity on either side of it. It can be employed to contain the gas being analyzed or to store, under standardized conditions, nitrogen or other unabsorbable gas from a previous analysis. The apparatus may be employed in three different ways: (1) Stop-cock B may be placed in position BW (see Fig. 2), thus disconnecting the smaller burette; the larger may then be used as an ordinary Haldane analyzer. In this way volumes of about 16 ml. with absorbable gases amounting to 25 per cent of the total can be analyzed. The analysis can be made with the same speed and precision as in the ordinary Haldane analyzer. (59 The stop-cock B may be placed in position Bl; excess nitrogen may be expelled from both the larger and smaller burettes, which can then both be filled with the unknown gas. The volume thus taken for analysis can be as large as 28.5 ml., with a consequent gain in accuracy though with a loss in speed. Such analyses can be made provided that 12 ml. of the total are ultimately left unabsorbed. Therefore mixtures containing over 57 per cent of absorbable gas can be analyzed. (3) The third method is that for which the apparatus was primarily designed. Following an analysis of air, 12.5 ml. of residual nitrogen are transferred to the smaller burette (2) in which the nitrogen is stored to assist in the following analysis. The volume so stored is carefully balanced against the control tube (3) in the ordinary way immediately before any further excess of nitrogen is ejected. In such a balancing cock B is obviously in position Bl. When balance is attained, cock B is first turned to position B2; then and then only is cock A turned to position A2, the excess nitrogen is ejected, and the new gas introduced. When the new gas has been introduced, cock A is returned to position Al and cock B to position Bl before the volume of the gas introduced is read. During the analysis the nitrogen stored in burette (2) is added as required to that in burette (1). Consequently, any gas of any volume up to 16 ml. can be manipulated, even if 100 per cent of the gas is absorbable. It is often convenient to be able to analyze a sample below the

4 84 Modified Haldane Gas Analyzer normal volume (e.g., of 8 ml.). This also can be done without modifying the procedure, though naturally with some loss of accuracy. Apparatus Utilized As a Single Burette-The arrangement may best be seen in Fig. 1. The entrance cock through which the gas is introduced (A) is of the type used by Grollman. At the end of an analysis this cock is in position Al (see Fig. 2) ; it is turned to A2 to allow the discharge of excess nitrogen; it is then turned to A3 to allow the connecting tubing to be washed out with the gas to be analyzed. It is returned to position A2 for the introduction of the gas and to Al for analysis. If the lower cock B be retained in position B2, then burette (1) may be utilized as an ordinary Haldane analyzer and all analyses proceed in the orthodox manner. When the nitrogen is discharged, the mercury meniscus is brought to the zero mark at 6; above it is 1 per cent sulfuric acid sufficient to reach almost to the side branch of the cock B, but not beyond it. The gas introduced is equal to the volume from the zero graduation to the ultimate position on the scale, plus the volume contained in cock A. This cock originally contained nitrogen but finally contains the gas under analysis. The precautions to be taken in relation to the control system are described later. When the single burette is used in this manner as an ordinary Haldane apparatus, analysis of outside air, expired air, and the like can be conducted with speed and accuracy. There is some gain in accuracy from the larger volume utilized and some loss through the complications of the dead end of the T-cock B. A typical set of successive analyses of outside air in triplicate by this technique is given in Table I in Section A. Use of Both Burettes to Accommodate Unknown Gas-In this case the introduction of the gas proceeds as before but cock B is in position Bl throughout, and nitrogen is expelled also from burette (2). The mercury meniscus in the smaller burette is also brought to the zero mark D; 1 per cent sulfuric acid fills the top part of the burette up to, but not into, stop-cock B. The total volume is taken into both burettes (up to a volume of 28.5 ml.). In gas absorption the mercury in burette (1) is alone used as a pump. The gas in burette (2) is merely forced up by the mercury to join that in the other burette. When the connecting tubes

5 H. C. Bazett 85 are washed out when the gas is being fetched from the carbon dioxide absorber and the like, the absorption of gases may be speeded by reversing the columns of gas contained in the two burettes. Thus the last gas from the oxygen absorber may be taken into burette (2) which will thus contain pure nitrogen, if air is being analyzed. When the gas is returned to the ab- TABLE Consistency Obtainable in Successive Analyses in Triplicate I Gas analyzed Outside A. With burette (1) only air Means... y?y B. With both burettes for un known gas Means... C. With burette (3) to store N Means...,... Tank D. With burette (2) to store oxygen Nz under steady room conditions ml. co, per cent per cent N2 YJer cent Means sorber, the gas from burette (1) may be passed first, and the pure nitrogen in burette (2) be used to wash it further into the absorber. The accuracy thus obtainable in the analysis of air is illustrated by the successive analyses in triplicate given in Section B of Table I. An analysis takes about 15 minutes. Use of Second Burette As a Store for Nitrogen--In the third

6 Modified Haldane Gas Analyzer method of use nitrogen at the end of an analysis is moved from the bulb of burette (1) into the CO2 absorber and then is taken into burette (2). Any excess nitrogen is taken into the bulb of burette (1). (Great care must be used for the balancing point may be at a position where the mercury is in the center of the larger bulb.) Cock E on the control tube is then opened to the air and the control system is brought precisely to atmospheric pressure, while the gases in the two burettes are balanced against it. Cock E is then closed, the balance is rechecked, and minor adjustments are made if needed. Cock B is then turned from Bl to B2, then cock A from A1 to Ad, and the excess nitrogen is ejected as usual. When the new gas has been introduced and cock A has been returned to position Al, cock B is returned to the Bi position before balances are attained and volumes read. When these readings are made, care must be taken to insure that there is no water-lock produced by a bubble in cock B. Such a lock is readily formed if the 1 per cent sulfuric acid in either burette is slightly in excess and reaches the branching of the T-cock. If the machine is reasonably clean, such a lock, if formed, can readily be broken. After the volume is read, the gas in burette (1) is absorbed, and nitrogen is added to it from burette (2) as required. The nitrogen may be used to wash the absorbable gas into the absorbing solution. The pumping action in burette (1) may be conducted with cock B in either position Bl or BW, according to the analysis being made. If the cock is in position Bi, the mercury in the burette should be at the zero position. The accuracy obtainable with such procedures is indicated in the successive triplicate analyses of outside air shown in Section C of Table I and of tank oxygen shown in Section D of Table I. The greater accuracy is normally obtainable with the lower percentages of absorbable gas. The slightly greater accuracy shown in Table I for analysis of tank oxygen is due to the analyses having been conducted when the room temperature was particularly stable, while those for outside air were made under ordinary conditions. As will be explained, analyses of pure oxygen (or of carbon dioxide) are particularly liable to errors due to changes in temperature, and for maximal accuracy temperature fluctuations should be kept small. In spite of this, under ordinary conditions

7 H. C. Bazett errors should never exceed 3~0.05 per cent. The time consumed in using the analyzer in this way is also about 15 minutes per analysis. Technical Details-The difficulties and pitfalls will be readily recognized by those familiar with gas analysis. The compensation for temperature changes attainable from the dummy burette is only accurate if the ratio of the gas contained in the tubes within the water bath to that contained in tubes in air in the active system is the same as the ratio of these two sets of tubes in the control system. Obviously these conditions cannot be met exactly, since the ratio of the gas contained in the tubes in the water bath to that in the connecting tubes in the active system is constantly changing during the course of an analysis. The larger the proportion of absorbable gas, the greater is this change and the less accurate is the compensation attained. The maximal compensation will be attained if the ratios are comparable during the relatively slow process of the removal of the last traces of oxygen. For this reason the control burette (3) is made of simple tubing of 5 to 6 mm. bore and is fitted below with a stop-cock and a mercury reservoir. When the machine is standardized, not only are the various calibrations exactly checked but also the optimal positions are determined for the water meniscus above the mercury in this control tube to attain compensation for any given volume in the active burettes. This is done empirically by setting the water level in the control burette (3) opposite some given position on burette (1) and determining the apparent change in volume of burettes (1) and (2), when the water bath is either cooled or warmed. These determinations are made with various volumes in burettes (1) and (2). The optimal position for the fluid level in the control system is thus determined empirically; such determinations made on five or six different volumes in the active burette allow a curve to be drawn. The control tube can then be set at its optimal position for any given set of analyses. Even so, if the changes in volume are great (as in analysis of tank oxygen), compensation attainable towards the end of the analysis implies that it is inadequate at the start and that estimates of CO2 concentrations may be slightly in error. (It may be noticed in Section D of Table I that the discrepancies were regular and progressive-

8 88 Modified Haldane Gas Analyzer their direction could be predicted from the direction of the slight temperature changes.) The adjustable character of the control tube is a definite advantage and one which can readily be incorporated in any Haldane analyzer. Anyone undertaking the use of an analyzer of this type should be warned to be particularly careful if precision is needed in the analysis of pure oxygen. Under such conditions there is little or no nitrogen available to expel through cock A before the new sample is taken in. It is consequently imperative that this process be carried out very carefully, so that the connecting tubes between the burette and the exterior do not get prematurely fouled by the incoming air. At the time cock A is turned to position A2 the pressure in burette (1) must be slightly greater than atmospheric and a slight amount of nitrogen must be available for expulsion. Even when larger volumes of nitrogen are available, the system should be carefully balanced against real atmospheric pressure before cock E is closed and nitrogen is expelled, as already explained. There is a volume of gas existing between the zero point C (or in the second method from zero points C and D) and cock A, consisting of nitrogen maintained in the system and measured against the balance of control burette (3) ; yet when cock A is open, this gas can freely escape if the pressures within and without the system are not the same. The volume of this gas is small; it can be reduced to negligible proportions by using fluid above the mercury adequate to reach up to but not into cock A. If cock B is kept exceptionally clean, this may be done without difficulty, but if cock B becomes greasy, troublesome water-locks readily form. In standardization of the calibrations particular care must be taken to use the burettes wet and to move the mercury as it is moved during an analysis. The water in burette (2) tends to collect in the lower bulbs and to rise to the top only slowly if the mercury is brought up rapidly in this irregular system. In use the movements of the mercury should be controlled by the cock so that the mercury only rises at a moderate speed. Standardization should be made with the same rates of movement. The ease of handling and the accuracy of the machine are obviously improved if the volume between cocks A and B is as small as possible.

9 H. C. Bazett 89 I would like to pay tribute to the skill and care of Mr. James D. Graham, of the University of Pennsylvania, who built the two cocks with a length of only 6 mm. of capillary tubing between them. SUMMARY A modification of the Haldane gas analysis apparatus is described. This modification is adapted to allow analysis of samples of gas up to 16 ml. from mixtures containing up to 100 per cent of absorbable gas. This is attained by using a main burette of 16 ml. with 4 ml. graduated in 0.01 ml., and a second burette connected to it by a T-cock containing 12.5 ml. The latter burette may be used to store nitrogen, which can be accurately measured and be utilized to make up the volume in the main burette as gas is absorbed. The smaller burette consists of three sections with a bulb of 3.5 ml. and a graduated tube above it of 0.5 ml. Below the lowermost bulb an additional 0.5 ml. is graduated. The accuracy obtainable is of the same order as that of the ordinary Haldane apparatus. The double burette can be used not only in this way but also both burettes may be used to contain the unknown gas. Samples of gas up to 28.5 ml. in volume may thus be analyzed if the absorbable gas is 57 per cent or less of the total. The accuracy obtainable in this form in analysis of outside air is of the order of f0.005 per cent. If desired, the main burette alone may be used exactly as an ordinary Haldane analyzer. Owing to the very variable volumes that may be utilized in the active burette, it is important to have the volume of air in the control burette adjustable. The arrangement for so doing is described, and it is pointed out that it is a useful addition to the ordinary Haldane analyzer.

10 A MODIFIED HALDANE GAS ANALYZER FOR ANALYSIS OF MIXTURES WITH ONE HUNDRED PER CENT ABSORBABLE GAS H. C. Bazett J. Biol. Chem. 1941, 139: Access the most updated version of this article at Alerts: When this article is cited When a correction for this article is posted Click here to choose from all of JBC's alerts This article cites 0 references, 0 of which can be accessed free at ml#ref-list-1