RICHARDSON ON M E T H O D S FOR T E S T I N G A M M O N I A . on the crucible and both are transferred to a desiccator to cool. Li’hen cooled, weigh and subtract the weight of the crucible and lid from the weight of the same with contents. This gives the weight of iron oxide (Fe,O,) contained in the crucible. This is calculated to metallic iron, viz. : 160 : 1 1 2 = wt. Fe,O, : x wt. Fe. The percentage of cloth in the plaster has been determined as above in other piece of plaster, therefore the weight of the piece of plaster ignited is multiplied by the per cent. figure for cloth, determined in the other piece of plaster. The weight so found is subtracted from the weight of plaster ignited, which result is the weight of compound ignited. The weight of Fe found, multiplied by IOO and divided by the weight of compound ignited, gives the per cent. Fe in the compound. To Arthur LT. Clark and Powell Hampton acknowledgment is due for work in the elaboration of these processes. I.ABORATORY OF
JOHNSON
& JOHNSON, J.
NEW BRUKSWICR, N.
METHODS FOR TESTING COMMERCIAL, ANHYDROUS, LIQUID AMMONIA. B y W.D. RICHARDSON. Received J a n u a r y 1, 1910.
The average refrigerating engineer is very critical of the quality of the anhydrous ammonia which he uses in his refrigerating system. If anything goes wrong with his plant he is very a p t to blame the ammonia, which he is using, for the trouble. These facts must be taken into consideration when an engineer criticizes any given brand of liquid ammonia. I t may be that the ammonia is not a t fault at all, but that bad management, bad operation or leaks are responsible for the trouble. Nevertheless; there is a certain amount of agreement among engineers all over the country as to the quality of certain brands of liquid ammonia sold for refrigerating purposes. This agreement is so general among engineers a t widely isolated points, that it must be given a good deal of consideration in forming a n opinion as to the quality of any given brands. Criticism of certain makes of ammonia were so persistent that it became necessary to investigate a number of different brands on the market with the idea of determining, if possible, what brand was best to use and what one worst for refrigerating purposes. The ammonias investigated mill be referred to by letters .4, B, C, D, and E, and the quality of the different brands was in the order given, A being the best and E the worst. To determine the residue after evaporation, USF was made of the apparatus described by Dr. F. W-. Frerichs. From one to five lots of 100 cc. each were evaporated slowly either in the air or in a calcium chloride bath, the * Tms JOURNAL, 1, 368 (1909)
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latter being used to avoid the accumulation of snow and ice on the bulb. The evaporation was conducted until the ammonia was boiled off, but no longer than this, when the volume of the ammonia was read off. The results by this method were as follows from 500 cc. of the liquid ammonia: “A,” 0 . 0 5 cc.; “ B , ” 0 . 0 5 cc.; “C,” 0 . 0 5 cc.; “D,” 0.07j CC. ; “E,” 0 . I O CC. These residues all consisted of dark oily-looking matter containing some iron oxide. The residue was darkest in the case of sample ‘ ‘ E ” and lightest in the case of “A,” and the colors were pretty well graduated from “ A ” to “E.” The amount of residue obtained indicates that the ammonia now sold on the market is nearly free from substances non-volatile at the temperature of boiling ammonia; but a most suggestive point in connection with these results is that many engineers a t different points from their experience with different makes of ammonia grade them just as they would be graded from the results of these evaporative tests, that is, engineers who have never made or seen any chemical tests in their experience would grade the various makes of ammonia from their experience just as they would be graded by these evaporative tests. I t was thought that some information as to the quality of the ammonia might be obtained by investigation of the non-condensing gases, or rather of the non-basic gases dissolved in the liquid ammonia. Among the non-basic gases would be included practically all of the non-condensing gases likely to be present and also carbon dioxide. For this purpose the drum was supported in the ordinary position for drawing off liquid, Frerich’s apparatus was attached for convenience in drawing off and the following apparatus was made use of: a 50-cc. gas measuring burette graduated in 1 / 1 0 cc., with stop-cock in the upper end, was sealed by its open end to the bottom of a flask of convenient size, say 1,000 or 2,000 cc. capacity approximately. This apparatus was filled with standard sulphuric acid of convenient strength, say -V/2, N or 2 AV, and inverted in the same acid contained in 1,000 or 2 , 0 0 0 cc. evaporating dish. The total volume of acid used is known; the acid is colored by means of cochineal indicator. A long narrow delivery tube of glass with end bent upwards is connected with Frerich’s apparatus by means of a strong piece of rubber tubing. The valves are now opened and a small quantity of ammonia allowed to pass through the delivery tube in order to clean i t out. While the ammonia is still issuing from the tube in a slow, steady stream i t is suddenly thrust under the gas-collecting apparatus ; the ammonia is allowed to pass into the standard acid until this is saturated, which is shown by the change of color of the cochineal indicator. The acid must, of course, be suitably agitated. A t the saturation point the tube is quickly withdrawn and the gases afterwards drawn off into a
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T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y .
Hempel gas-measuring bure‘tte and measured. The amount of ammonia drawn off is calculated from the amount of acid saturated, which may, of course, be any convenient amount, and the volume of gas obtained in the gas-measuring burette may be calculated to unit weight or volume of ammonia, whichever is desired. The results obtained by this method calculated in cc. of gas per gram of ammonia were as follows: “A,” 0.148 and 0.128; “B,” 0.124, 0.129 and o 107; “C,” 0.166 and 0.156; “D,” 0.163 and 0.139; “E,” 0.293, 0.328 and 0.313. These amounts showing the gas dissolved in the ammonia, while not very large, places the various brands of ammonia in approximately the same order that they are placed by operating engineers. Brands “ A ” and “ B ” are generally considered above criticism. Another method for determining the gases dissolved in the liquid ammonia is easily suggested. Instead of allowing the ammonia to pass into the standard acid to its saturation point, the delivery tube is removed before this point is reached. The gas collected is drawn over into a Hempel gas-measuring burette and measured and the standard acid made up to volume in a volumetric flask of sufficient size and a n aliquot titrated with a standard alkali. From the data so obtained the weight of ammonia drawn from the drum can be calculated. Next the non-basic, or, in other words, the noncondensing gases as ordinarily understood, lying above the liquid ammonia in the drum, were investigated. For this determination the same apparatus was used as in the previous determinations, but the drum was turned over and inclined slightly, so that the gas lying above the liquid ammonia might readily be drawn off. Following this the procedure was identical with that given above and the calculation was the same. “ A ” showed 0 . 6 , 0 . 3 , and 0 . 6 cc. per gram of ammonia; “B”showed 1 . 0 and 1 . 1 ; “C”showed 4.4, 3.8, 3.3 and 2.4; “ D ” showed 27.6 and 21.3; “ E ” showed 307 .o cc. and 330 cc. Thus in the gas lying above the liquid ammonia and calculated in cc. per gram of ammonia there are shown to be enormous differences in the different makes varying all the way from 0 . 6 of I cc. up to 330 cc. These non-condensing gases represent a considerable loss to the buyer at the outset, inasmuch as ammonia is tqken out of these drums under vacuum and any non-condensing gas taken into a n ammonia system must be blown off sooner or later, and when blown off it will carry with it a certain amount of ammonia. Further, in the operation of the system non-condensing gases are probably the greatest evil, since they reduce the partial pressure of the ammonia gas in the condenser, and thus tend to elevate the pressure and the temperature of the comhressor cylinder. Thus the efficiency of the compressor is greatly reduced, and i t is possible too that with the higher pressures, the higher
Mar., 1910
temperatures required to get the same capacity out of a compressor may result-in the actual decomposition of ammonia or lubricating oils. I n order to get a n idea of the direct loss to the buyer of these noncondensing gases, a drum of ammonia was balanced on a small platform scale in a n inverted position, so that the gas lying above the liquid ammonia could be drawn off, use was made of Frerich’s apparatus connected to a long, narrow’ .delivery tube and the gases were drawn off into tubs of cold water until all of the issuing gases were absorbed by cold water or acid, thus indicating that nothing but basic gases, or practically pure ammonia, was coming off. The drum was then weighed back andithe loss figured. This loss, of course, included not only the non-condensing gases but also ammonia itself. However, the same loss of ammonia would result when non-condensing gases are blown off from the ammonia system. Under this test brand “ A ” showed no loss, that is, the loss was too small to be weighed on the scale used; brand “ B ” showed a loss of 1/4 lb. to the drum; brand “ C ” showed a loss of I l/* Ibs. per drum; brand ‘ID” showed a loss of 41/2 lbs. per drum; brand “ E ” showed a loss of 3 lbs. per drum. Here again there is a rather startling dSerence between different makes of ammonia. The writer does not want to suggest that all the troubles in the refrigerating plant are due to non-condensing gases coming from the drum of ammonia used, but that these gases can and do cause trouble in a system there should be no reasonable doubt. Further, that liquid ammonia can and should be made free from such gases is also beyond question. Analyses of the non-condensing gases from the various drums were made b y Hempel’s methods and it was found that these gases consist for the most part of air with, however, a lower percentage of oxygen than corresponds to atmospheric air. It is possible, and not unlikely, that some of the oxygen has been used up in the oxidation of lubricating oils or the oxidation of the drum or other metal parts of the manufacturing apparatus. Hydrogen is present only in small quantity, the percentage found being 3 per cent. A sample of gas taken from the top of the condenser of a well-regulated and well-operated ammonia plant, in which no high pressures or temperatures had been recorded for a good many weeks, showed practically the same composition as the gases from the above liquid ammonia in the drums. As specifications for anhydrous ammonia? based on the results of this investigation, I should say that the total residue by the method described per IOO cc. of acceptable ammonia ought not to be greater than one-tenth of I cc. ; the non-condensing gases dissolved in the liquid ammonia ought not to be more than 0 . 1 2 of I cc. per gram of ammonia; the non-condensing gases lying above the liquid ammonia ought
ADDRESSES. not to be greater than 0 . 6 cc. per gram of ammonia; and the whole drum, when tested on a scale by the method described, should not show any appreciable loss. It is possible that the amounts. of impurities here reported might not be regarded as serious by the makers of ammonia; however, this work establishes the fact that anhydrous ammonia is being made and can readily be made of the purity required by the specifications, and there is no reason why any ammonia should be sold which does not come up to these standards. T h a t a good deal of trouble is caused in refrigerating plants by the ammonia used there can be no question, because the universal testimony of reputable engineers is to this effect. T h a t a part of i t a t least may be due to non-condensing gases in the drum is easily believable. LABORATORY OF SWIFT & Co CHICAGO,ILL.
,
ADDRESSES. -__
T H E IMPROVEMENT OF ANALYTICAL PROCESSES.’
4
B y W.D . RICHARDSON. Following Bergman’s suggestions and the prominent and successful use of the chemical balance by Lavoisier, the art of quantitative chemical analysis developed with fair rapidity, until in the early half of the nineteenth century many chemists were adept in it. Practically all of this development came through individual effort and experience. There was practically no concerted action, little cooperation in the development of methods of analysis. One by one the methods were developed and put upon a working basis. They were systematized and systems of mineral analysis appeared. Qualitative analysis was developed to a high point of perfection, already in the forties of the nineteenth century. A fair system of quantitative mineral analysis was developed and used not many years later. From this beginning quantitative analysis developed more and more along the line of special methods, assay methods, they might be called, where one constituent only was sought for among all that might be present; and the methods tended more and more to attain speed without sacrificing accuracy. I n the end analysis became more and more a matter of formula and less and less a matter of carefully thought-out plan on the part of the analyst performing the work. Fresenius foresaw that quantitative analysis might take this turn and repeatedly warned the student to plan his work carefully before commencing operations. Analysis is the distinctive a r t of chemistry, and chemists must universally regret a decline of the art, yet we must acknowledge t h a t there has been a decline t o a greater or less extent which has accompanied the reduction of analytical processes to recipes and formulae. Because it was possible to teach a boy of no special education or preparation one or more methods of chemical analysis, so t h a t he could perform the operations and obtain good results, the chemist came to look upon analysis as a more or less perfunctory and disagreeable duty which he was called upon from time to time to perform. This was particularly the case and is still the case to a large extent, because of the applications of chemistry to manufacture and engineering, xi7hich to many a t the present time appear t o be nobler and higher callings than that of analytical chemistry. 1 An address before the Division of Fertilizer Chemists, -4merican Chemical Society, Boston meeting, December, 1909.
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With the decline, as I call it, of the a r t of analysis came the realization on the part of many chemists that steps must be taken to insure accurate results in chemical analysis at all hazards, because it was seen that inaccuracy prevailed far too widely in the work. I n the eighties, in this country, the work was taken up systematically, particular credit being due to the American Association of Official Agricultural Chemists, who first investigated the methods of analysis as applied to fertilizers, and formulated methods of analysis which would yield, in average hands, good results. Their efforts were eminently successful, and while we must agree at the outset that no amount of care in formulating methods can take the place of good analysts and accurate manipulation, nevertheless the former are necessary forerunners of good results. The procedure used by the A. 0 . A. C. and by other organizations in dealing with analytical methods characterize the present time in analytical chemistry. IVhile the invention of new analytical methods by individuals will still continue, nevertheless the working out of these methods, their standardization, is being done now and will be done in the future by committees and the collaboration of many chemists. Since this is the tendency of the present times, it may be well to consider the important features of the work as now performed. I n the first place, the dictum that chemical matters should be handled by chemists will hardly be gainsaid, certainly not by one of the profession. It is only equivalent to saying that legal matters should be handled by lawyers and medical matter by physicians. I t happens in the case of the chemical profession that applied chemistry is a large factor in many manufacturing lines and that manufacturers and associations of manufacturers are largely interested in analytical processes. It also happens that the manufacturer dealing with chemists under his control and commercial chemists outside of his line has returned to him every now and then results which lead him to lose faith in chemists and chemical processes. This usually happens m-hen he sends out the same sample to different chemists and has different results returned. Such results lead him into action looking like self-protection in similar cases and to the improvement in some way of existing conditions, so that such things may not recur. H e may correspond with one or all of the chemists and ask for explanations. This will probably be his first step. He will probably also avoid as much chemical work as possible in the future and he may request the commercial organization t o which he belongs to investigate the matter. That organization, in its investigation, may appoint a committee t o consider the methods which chemists are using for certain determinations, and this is the point about which I wish to speak particularly. It seems as though the appointive powers of committees interested in the investigation of chemical analysis or any chemical matter ought to rest with responsible chemical organizations. As I see it, the manufacturer or chemical association’s committee ought t o go no further than to lay the whole matter before the proper chemical society and ask for action. I t goes without saying that a chemical society to whom such matters are referred should extend friendly and accurate assistance to the adjustment of the difficulty, and t o the matter of the criticized processes. As to the association or society of chemists which should take such matters under consideration, I have nothing further to suggest than that they should be truly representative, and by representative I mean that any chemist interested in the particular field concerned should be eligible to membership. This has been the only serious criticism and drawback to the work done by the A. 0 A . c . Many chemists interested in a particular line of work, whether fertilizer or food work, are excluded from this association. The answer to this may be that the methods developed by the A. 0. A. C. are developed principally for guidance of their own
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