Licence: In copyright
Credit: Naval hygiene / Henry G. Beyer. Source: Wellcome Collection.
Provider: This material has been provided by London School of Hygiene & Tropical Medicine Library & Archives Service. The original may be consulted at London School of Hygiene & Tropical Medicine Library & Archives Service.
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![Naval Hygiene. Table IV. Number of Volumes Number of Volumes tlllings. per 1,000. fillings. per 1,000. 48 0.3 8 1.3 35 .4 7 1.4 27 .5 6 1.5 21 .6 5 1.8 17 .7 4 2.1 10 .9 3 2.5 9 1.0 2 3.0 More recently still a neat and liandy method similar to the preceding, and based on practically the same princi- ples, has been devised by Dr. G. W. Fitz. This method is carried out by shaking a small quantity of dilute lime water, colored piuk with phenolphthalein, with succes- sive portions of air until the solution is decolorized. The metliod has of late been made still more practicable by Woodman and Richards {Technology Quarterly, vol. XIV., No. 2, June, 1901). Since I have used this method quite a little and have found it to answer every purpose on board ship, being easy of application, also sufBcientlj^ accurate, a detailed description, given by Woodman and Richards, will here follow: Description of Metlwcl of Using the Shaker for Determin- ing the Amount of Carhon Dioxide in the Air.—The method of preparation of the solutions and the manner of making the tests which have been foimd to give the best results will be described in detail, since experience has shown that these directions cannot be too minute. Preixiration of the Test Solution.—The solution used is a dilute solution of lime water colored witli phenol- phthalein. To freshly slaked lime add twenty times its weight of water in a bottle of such size that it is not more than two-thirds full. Shake the mixture contin- uously for twenty minutes, and then allow it to settle over night or until perfectly clear. The resulting solu- tion is the stock lime solution, or ' saturated lime water.' If made in the manner indicated, each cubic centimetre of it ought to be very nearly equivalent to 1 mgm. of carbon dioxide. If, however, it is desired to know the .strength of it more exactly, it may be determined by standard acid. To prepare the 'test solution,' pour into the 1-litre bottle of the testing apparatus one measured litre of dis- tilled water, and add 5c.c. of solution of phenolphthalein (made by dissolving 0.7 gm. of phenolphthalein in 50c.c. of alcohol and adding an equal volume of water). Stand tlie bottle on a sheet of white paper and add the ' satu- rated lime water,' drop by drop from a pipette, shaking the bottle tlioroughly after each addition, until a faint pink color is produced which is permanent for one min- ute. Now add 12.6 c.c. of the 'saturated limewatei-,' shake, and immediately connect the bottle again to the apparatus. Table A. Standard test solution. CO2 in 10,000. Cubic centimetres of air. Half solution. in 10,(XI0. Standard test solution. CO2 in 10,000. Cubic centimetres of air. Half solution. CO2 in 10,000. 22.3 .50 15.6 S.9 370 4.1 18.0 70 13.4 5.6 290 3.95 15.1 90 10.2 5.4 310 3.8 13.0 110 8.7 5.1 330 3.7 11.3 130 7.5 4.8 3.50 3.6 9.9 150 6.6 4.7 370 8.8 170 5.8 4.5 390 8.0 190 5 2 4.4 410 7.3 210 4[8 4.3 450 6.8 330 4.5 4.0 490 6.3 2.50 4.3 3.9 530 To shorten the time required in testing air which is low in carbon dioxide, it may be found advantageous to use a solution only half as strong as the above. This 'half solution ' is prepared in precisely the same way, Voi>. VI.—11 Fig. 3.504.—The Fitz Shaker, Full Size. (From Woodman and Richards.) using 2.5 c.c. of the phenolphthalein solution and 6.3 c.c. of the 'saturated lime water.' While this procedure does not give an exact volume of solution, it is believed to be the best for the prepara- tion of this dilute test solution, since it obviates the nec- essity for pouring tlie prepared solution from the measur- ing iiask into the bottle in which it is kept; 12.6 c.c. of the stock lime solution is added rather than 10 c.c, in order to keep the values obtained with the re- sulting solution more nearly com- parable with the older values cal- culated on the supposition that 10 c.c. of 'saturated lime water' was equivalent to 12.6 mgm of carbon dioxide. Method of Makiiig the Test.—See that the inner tube of the shaker slides readily iu the outer one, moistening the rubber collar slight- ly if necessary. Have the inner tube pressed down to the bottom uf the larger one, and measure into the apparatus 10 c.c. of the test solution from the automatic pipette. Pull the inner tube up to the 5 c.c. mark (the bottom of the inner tube serving as the index) and close the end of the tube with the finger. Hold the apparatus horizontally, and shake it vigorously for exactly thirty .seconds. The amoiintof air which is thus brought in contact with the solu- tion is equivalent to 30 c.c, as there are 25 c.c of air above the liquid when the small tube is forced to the bottom of the larger. Remove the finger, press- down the small tube again to the bottom of the larger and draw it up to the 20 c.c. mark. Shake the appa- ratus again for thirty seconds. The amovmt of air brought in contact with the solution is now 30-1-20 = 50 c.c. Repeat the shaking, using 20 cc. of fresh air eaclt time until the pink color is discharged. The amount of carbon dioxide corresponding to the number of cubic centimetres of air used will be found in Table A. '''Notes and Precautions.—Care should be taken that the linger used to close the end of the tube is perfectly clean, since on a warm day the free acid in the perspira- tion might easily vitiate the results. If greater accuracy is desired, the shaker should be filled with the air to be tested before running in the test solution. This may be done readily by filling the shaker with water and emptying it or by forcing air into the tube by means of a small rubber bulb. The apparatus should be shaken vigorously and con- tinuously during the thirty seconds in order to absorb ]:)ractically all of the carbon dioxide in 20 c.c. of air. The number of shakings ought not to be less than one hundred during this time. Care should be taken not to contaminate the air while the sample is being taken. The breath should be held momentarily while the air in tlie apparatus is being I'e- placed, and the samijle should be collected as far to one side of the body as possible. It ought not to require over ten seconds to replace the air, and the entire test, with air containing, say, 8 parts of carbon dioxide per 10,000, should not require over six minutes. It less than 90 c.c of air is required to discharge the pink color, the test should be repeated, using 10 c.c. of air each time after the first 30 cc. It is not necessary to rinse out the shaker after mak- ing each test, but it should be carefully washed and dried after using, and the parts kept separate when not in use. The ' half-solution ' is used in exactly the same man- ner and amount as the regular test solution, reference being made to the appropriate portion of the table. A ir Qua.ntitm Needed.—The ventilating plant to be de- signed for a place or ship must be given a ventilating](https://iiif.wellcomecollection.org/image/b21360315_0013.jp2/full/800%2C/0/default.jpg)
