This additional apparatus can also be obtained in a small compact box, with handles attached, which can conveniently be carried to the desired location.

QUANTITATIVE DETERMINATION OF CARBON MONOXIDE IN BLOOD

The only infallible diagnosis of carbon monoxide poisoning is made by examination of the blood for carbon monoxide-hæmoglobin (CO-Hb), the compound that carbon monoxide forms with blood and through which it possesses asphyxiating properties, already discussed. If this test is made it indicates the seriousness of the case and provides a just basis for treatment; also, it often obviates litigation and insures justice in medicolegal and compensation cases. A mere qualitative examination for this compound will indicate whether or not carbon monoxide is present, but to know whether or not carbon monoxide is the primary cause of the condition of the patient it is necessary to make a quatitative determination of the CO-Hb present.

The following procedure for sampling and testing blood for carbon monoxide is based on the apparatus described, but it may be modified to suit facilities at hand:

1. A small puncture wound (approximately 2 mm. deep) is made with the hæmospast in the tip of the finger of the victim, or suspected victim, of carbon monoxide poisoning, and several drops of blood are caught on the spot plate or drawn directly into the pipette. If the blood does not flow freely, the finger is wrapped with the rubber hose, beginning at the base and progressing toward the tip; massaging the finger also aids the flow. (If death has intervened, it may be difficult to obtain liquid blood, but this usually can be done during embalming.)

2. When the blood has been produced, it is quickly drawn into the stem of the pipette to the 0.1 c. c. mark.

3. The pipette is then held horizontally, and any blood on the exterior of the tip is removed.

4. The tip is raised slightly to allow a little of the blood to flow into the diluting bulb.

5. Inserting the pipette quickly into the bottle of water and using suction at the same time it is filled to the 2 c. c. mark to give proper dilution.

6. The blood solution is now discharged into one of the test tubes, a little of the solution being drawn back once or twice into the pipette to wash out any adhering concentrated blood. (NOTE: To eliminate possible clotting the entire procedure of obtaining the blood specimen should be as rapid as possible.)

7. If it is desired to take more than one sample the pipette should be rinsed out with water, the capillary stem blown free from water, and the tip of the pipette dried before the next sample is obtained.

8. Immediately after the blood solution has been discharged into the test tube approximately 0.04 gram of the pyrogallic-tannic acid mixture is added, and the tube is gently inverted several times to insure thorough mixing with the reagents.

9. The tube is then placed in the rack and allowed to stand 15 minutes at room temperature. (If particles of the solid acids settle out, the tube should be inverted several more times.)

10. At the end of the 15 minutes the tube containing the sample is compared with the standards by interposing it between them until the standard is found which most nearly matches it.

11. If carbon monoxide is indicated, the sample should be allowed to stand 15 minutes longer and another reading made. The latter reading should be taken as the more accurate.

12. The percentage of the carbon monoxide-hæmoglobin (CO-Hb), or what is termed "blood saturation," is estimated from the value of the standard that most nearly matches the specimen in the test tube. The comparison of the tube containing the sample with the standards is best made in daylight but not in direct sunlight. The observer should stand with his back to the light, viewing the tubes by reflection, and should change position several times to note any dif ference due merely to unequal lighting effect. Observations may be made after several hours without serious loss of accuracy, although this is only advisable in case of necessity. The blood saturation of a victim of carbon monoxide poisoning can not be used as a means of determining the amount of carbon monoxide that was present in the air breathed by the victim. The duration of exposure, physical exertion, physical condition, and personal idiosyncrasies of the victim all are factors in the blood saturation, therefore blood saturation has no value as an indicator of the amount of carbon monoxide to which the victim has been exposed.

QUANTITATIVE DETERMINATION OF CARBON MONOXIDE IN AIR

The pyrotannic acid method is valuable in determining the amount of carbon monoxide in the blood of a victim of carbon monoxide poisoning. However, it is still more valuable to mining men as a device for determining the amount of carbon monoxide in the air. There are numerous occasions during known or suspected mine fires and after the sealing of mine fires when a method for accurately showing low percentages of carbon monoxide is of utmost importance. Many incipient mine fires could be prevented from reaching serious

proportions, with consequent loss of property and even of lives, if an efficient means of detecting low percentages of carbon monoxide is employed. The presence of carbon monoxide in the return airway of a mine is almost a sure indication of fire. Several mine disasters have caused loss of life because sealed fire areas have been opened before the fire was completely extinguished. Some of these might have been prevented had the composition of the air behind the seals been determined, especially as to its carbon monoxide content.

The pyrotannic acid method is particularly adapted to rapid and accurate determination of small amounts of carbon monoxide in air. It will not indicate more than 0.2 per cent. However, if more than this amount is present other means of detection can be employed, such as the hoolamite detector or sampling and analysis. In the range of low percentages from 0.01 per cent to approximately 0.2 per cent the pyrotannic acid method is very accurate, and for this reason it is used in preference to other methods or apparatus by the gas laboratory of the Bureau of Mines experiment station at Pittsburgh, Pa., for determining or confirming the presence of low percentages of carbon monoxide in samples of mine air, especially mine-fire atmospheres. The presence of carbon monoxide, even in a minute quantity behind fire seals, is always a strong indication that the fire is still burning, or at least has been burning too recently for the area to be opened with safety. It is in work such as this that the pyrotannic acid method shows its greatest value to the mining industry. The following procedure is outlined for determining the amount of car bon monoxide in air:

1. Samples of air are obtained by inserting the glass tube on the end of the scrubber into the sample bottle and aspirating the air through the sample bottle long enough to purge it of its original contents; this requires at least 25 squeezes of the bulb.

2. The last bulb full of gas should be expelled through the sample bottle while the glass tube is being removed, then the rubber stopper should be inserted quickly and tightly. If regular sample bottles and bulbs are not available, the samples may be collected in any ordinary bottle having a capacity of about 250 c. c. They may be filled with water and then emptied at the place of sampling. The walls should be well drained, as an excess of water will interfere with the accuracy of the result.

3. The collected samples should then be transported to the place for making the analysis, usually away from the place where the sample has been taken.

4. The blood to be used in making the analysis may be taken from a stock solution of relatively fresh human or animal blood or from a person, as previously described in obtaining blood for the

determination of carbon monoxide in blood. The blood must be obtained from a person who has not been exposed to carbon monoxide.

5. Dilution of the blood is made 1 in 20, as described for analysis of blood.

6. The 2 c. c. of blood solution is now introduced into the sample bottle, manipulation being such as to allow as little gas as possible to escape. (Note: Usually it is best first to discharge the solution. from the pipette into one of the small test tubes and to pour from this into the sample bottle.)

7. After the solution has been introduced into the sample bottle and the stopper tightly replaced the bottle is held horizontally and rotated constantly for 15 to 20 minutes, avoiding violent shaking and agitation.

8. After about 15 to 20 minutes, when equilibrating has been finished, the solution is poured back into the test tube, the pyrotannic acid added, and the comparison with the color standards made according to the procedure already described for blood analysis.

9. Equilibrating should be done in a rather dimly lighted place. When rotating the sample bottle, as much of the surface of the bottle as possible should be covered with blood solution. Every now and then the solution should be centrifugally thrown from the sides to the bottom of the bottle by a quick swinging motion, which allows a new surface to be formed and aids in reaching equilibrium. When a great many samples have to be analyzed, a motor-driven equilibrator will save time.

10. To transpose the amount of blood saturation obtained in the sample bottle to the percentage of carbon monoxide in the air, several formulas are used. To simplify the operation of making calculations and applying corrections for carbon monoxide in air, the curves in Figure 20 have been prepared. These graphically represent the calculations and corrections, and by following the instructions given thereon the corrected result of carbon monoxide in air for the blood saturation obtained in the sample bottle can be easily and quickly determined.

The pyrotannic acid method is a quick, efficient, and accurate means for determining the amount of carbon monoxide in blood and air. It especially indicates low percentages of carbon monoxide and is light, compact, simple, and easy to operate. It is well suited to the needs of hospitals, industrial surgeons, coroners, boards of health, departments of public safety, mine officials, mine inspectors, and safety engineers.