ANALYTICAL EDITION
98
of the sea biological activity or other factors may affect the calcium content of the water to a measurable extent. Further investigation of this subject is desirable and may throw some light on certain geological and biological phenomena taking place in the sea.
SUMMARY A micromethod for determining calcium has been adapted to the analysis of sea water and the technic is described in detail. The method is comparatively rapid and is capable of an accuracy of about 0.5 per cent or better. The results of calcium determinations on sea water from
Vol. 5 , No. 2
various depths are reported. These results confirm the conclusion drawn by previous workers that in sea water calcium is one of the substances present in constant proportion of the total salt.
LITERATURE CITED Dittmar, W., “Voyage of H. M. 8. Challenger,” Phys. Chem., 1, part I, p. 1, Edinburgh, 1884. (2) Kirk, P. L., and Schmidt, C. L. A., J. Bid. Chem., 83,311 (1929). (3) Poooff. S.,Waldbauer, L.. and McCann, D. C., IXD. ENG.CHEM., Anal. Ed., 4, 43 (1932). (4)Thompson, T. G., and Wright, C. C., J. Am. Chem. Soc., 52, 915 (1)
(1930).
RIUCEIVPD October 17, 1932.
Relation between Volume of Respiration Chamber and Concentration of Carbon Dioxide in End Sample and in Composite Sample of Air M, KLEIBER,Division of Animal Husbandry, College of Agriculture, University of California, Davis, Calif.
F
OR the measurement of the production of carbon di- carbon dioxide in a sample taken at a certain moment) the oxide and the consumption of oxygen, the subject author developed the equation in an earlier study (1). The of the experiment is either connected to or enclosed present paper shows that in many cases the composition of the in a respiration apparatus. The first method implies the composite sample is more important than that of the momenuse of a mouthpiece with nose clamp, as generally used on tary samples, and carries out the calculation for the influence humans for purposes of clinical research; or connection of the volume of the chamber, the rate of ventilation, and by means of a tracheotomy tube in the case of animals. For the rate of production upon the composition of the composite those experiments with animals in which tracheotomy is to be sample. An equation is given from which investigators in avoided, the second method must be used. The animal is this field can predict the influence of an error in gas analysis enclosed in a respiration chamber which is generally connected upon the error in the result for any apparatus. This is a guide for the selection of the apparatus for a given purpose. to a ventilating system. For the construction of a respiration apparatus for measuring the metabolism of animals, it is of interest to know the RELATIVESIGNIFICANCE OF MOMENTARY AND relation between the volume of the chamber, the rate of COMPOSITE SAMPLES ventilation, the rate of respiratory exchange, and the In an apparatus of the Tigerstedt type, a momentary concentration of the carbon dioxide and oxygen in the - sample is- t a k e n from the chamber. The d e g r e e of air in the chamber at the accuracy of the result of a beginning and at the end of t r i a l m a y t h e n be prea period, and a composite dicted, provided this degree sample which c o n s i s t s of is limited by the accuracy small a m o u n t s of the air of the gas analysis. taken regularly during the With a given rate of proe x p e r i m e n t is collected. duction in a chamber and The result for the carbon at a certain rate of ventiladioxide production is calcution, the concentration of lated according to the equathe product (for example, tion: c a r b o n d i o x i d e ) is t h e s m a l l e r , the l a r g e r the R = V(C, - Co) chamber. The knowledge LXtXC, of this general r e l a t i o n is, where however, i n a d e q u a t e for R = amount of carbon estimating the influenceof a dioxide produced certain error in gas anaIysis in the chamber upon the error in the result in liters V = volume of chamber of an experiment. For that in liters purpose the functions must L = intensity of ventilabe expressed in mathematition (liters per cal terms. The equations hour) t = time in hours for these relations seem not 0 Co = concentrationof to have been w o r k e d out. V O umc ~ of chamber in W m . carbon dioxide at For a p a r t of t h e p r o b thestart (momenFIGURE 1. INFLUENCE OF VOLUMEOF CHAMBER ON CONCENl e m ( c o n c e n t r a t i o n of tary sample) TRATION OF CARBONDIOXIDEAND RESULTING ERROR
+
March 15, 1933 C,
=
C,
=
INDUSTRIAL AND E N G I N E E R I N G CHEMISTRY
concentration of carbon dioxide at the end (momentary sample) concentration of carbon dioxide in the composite sample
The analysis of the composite sample becomes the more important the larger the amount of air sucked through (com-
Lt
pared with the volume of the chamber). The ratio - may be
v
called the relative significance of C, and (C, - CO)--i. e., the ratio of the amounts which are contributed to the result per unit of C, and (C, - CO),respectively. Thus, with a chamber of 10 cubic meters capacity and a rate of ventilation of 10 cubic meters per hour, the relative significance of C, and (C, - Co) would be expressed by the duration of the period in hours. For a period of 1 hour, C, would have the same significance for the result as (Ce - CO). If fe be the error of the difference (C, - CO),and f c the error of C,, the error of the result due to these errors in gas analysis would be
dfW.
If, under the same conditions, a period of 10 hours is considered, the significance of the analysis of the composite sample (C,) would be 10 times the significance of the difference between the analyses of the start and end samples (C, - Co). The error due to the error in gas analysis would If f i and f. are of the same magbecome df$2(1OfJ2. nitude,* it follows that for the 10-hour period, the error of (C, - CO) contributes only 1 per cent of the error of C,. On account of the dominating role of the composite sample for the result of experiments of long duration, the author has continued his earlier studies on the relation between the volume of the chamber and the concentration of the carbon dioxide in the momentary samples, and has also calculated the influence of the volume of the chamber on the concentration of the composite sample (Cm).
+
99
It follows from this equation that for a very small chamber Y (V +0), C,(,) becomes E. This is the case for the methods in which the animal is connected to, instead of enclosed in, the respiration apparatus. The result of this equation for a certain rate of production (c = 100 liters per hour) and a certain rate of ventilation ( L = 10 X l o 3 liters per hour) is shown as curve A , Figure 1. In order to calculate the influence of the volume of the chamber on the concentration of the carbon dioxide in the composite sample, the following procedure may be chosen: If v be the volume of the composite sample a t the time t, the amount of carbon dioxide in this sample will be C m X v. This amount is the summation of the small amounts dv taken a t regular intervals (which could be chosen indefinitely small). The amount of carbon dioxide brought to the sampler a t the end of the short period 1 will be C q ) X dv; the amount added during the period i will be Ce(i) X dv . etc., where C, is used as in equation 1, meaning the concentration of the carbon dioxide in the chamber a t a certain moment. The total amount of carbon dioxide in the composite sample, which is the product of the mean concentration C, and the volume, is the sum of all added amounts.
.. . . .
Thus C m X v = Ce(1) X dv
+ Ce(2) X dv + . . . . + Ce(i) X dv + . . . .
or
If s be the intensity of the air flow to the collector of the sample (presumed to be constant), the small increase of the sample dv is equal to s X dt and the end volume of the sample is v = s x t. If the values for v in equation 2 are thus subINFLUENCE OF THE VOLUMEOF THE CHAMBERUPON stituted, s is canceled out and it follows that COMPOSITION OF COMPOSITE SAMPLE The following equation was developed in the paper men(3) tioned above (1): Using the result for Ce from equation 1, the following equation is obtained:
where C, = concentration of carbon dioxide in air in chamber at end of period (liters of carbon dioxide per liter of air) Co = concentration of carbon dioxide in air in chamber at start of period ci
L V t y
concentration of carbon dioxide in air flowing from outside into chamber = intensity of ventilation (liters of air sucked out from chamber per hour) = volume of chamber in liters = duration of period in hours = intensity of carbon dioxide production in chamber (liters of carbon dioxide per hour)
C, =
$=" [
1 t
t=O
L Co X e - 7
z
+ + cd -
(z +
L ci)
e-
(4)
=
I n order to study the influence of the volume of the chamber on the accuracy of the result, the calculation may be simplified. The concentration of the carbon dioxide a t the start of the period and also the concentration in the inflowing air may be taken as nero. Thus, what is calculated is not the actual end concentration, but only that part of it which is due to the carbon dioxide production inside the chamber. The result of this simplification is
1 If the error in gas analysis is the same, the error of the difference of the two analvses (fi) .. .. is in fact not eaual to the error of the comuosite samule (to), but-fi is fc X 4 2 . The faitor, 4 2 , does not alter our conclusions and therefore has been omitted for simplicity.
t]dt
the integration of which leads to the following result:
(2 + 41( 7 L
c
--Yfci--
" - L
L X t
[c, -
With the simplifications made. above-namely and CO= 0-this equation is reduced to
1)
Ci
(5) =
0
The result of this equation for a period of 1 hour, a rate of production of 100 liters of carbon dioxide per hour, and a rate of ventilation of 10 cubic meters per hour as an example is shown on Figure 1, Curve B. The error of the result due to the errors in gas analysis is increased with the increase of the volume of the chamber. If the error in analysis of the composite sample is equal to 0.003 Der cent of the air volume, and the error in analysis of the difference between the initial concentration and end con-
ANALYTICAL EDITION
100
centration in the air of the chamber is equal to 0.004 per cent, then the error of the result will be *d(0.003
x
x
+ (0.004 x
or in the case shown on the figure ( t "dO.09
+ (0.004 X
=
x V)z
1, L = 10 X lo3) X V)2
Vol. 5, No. 2
Curve C on Figure 1 shows the increase of the error as the volume of the chamber increases according to the assumptions made. LITERATURE CITED (1)
Kleiber, M., Pjliigers Arch. ges. Physiol., 220, 599-605 (1928).
RECEIVED October 1, 1932.
Preparation of Aldehyde-Free Ethyl Alcohol Rapid Method ALBERTW. STOUTAND H. A. SCHUETTE, Department of Chemistry, University of Wisconsin, Madison, Wis.
C
URRENT methods for the preparation of waterwhite alcoholic potassium or sodium hydroxide sohtions are far from satisfactory, being not only uneconomical of time and materials but inconstant of performance in so far as they do not lead with certainty to the desired end. There is, therefore, an obvious need for an inexpensive method which will efficiently and rapidly remove the troublesqme aldehydes, to which, in virtue of .their forming brown resinous products with alkalies, the discoloration of the so-called alcoholic potash (or soda) solution is primarily ascribed. The m e t h o d s f o r accomplishing these ends are of two kinds, preventive and r e m e d i a l . I n the former group there are several which merit m e n t i o n . First, there is the timehonored procedure, to which both the Association of Official A g r i c u l t u r a l Chemists and the American Society for Testing Materials have given approval, of letting the raw alcohol stand in contact with potassium hydroxide for several days or of hastening the reaction by digesting the mixture for hours under reflux. Doubtless many an analyst following this procedure has been annoyed by the discovery that his labors have yielded a product of unsatisfactory character, a distillate FIGURE1. COMBI- which was obtained at some sacrifice NATION REFLUX AND DISTILLATION APPA- of expensive solvent, b e c a u s e of incomplete recovery of the solvent from RATUS the alkaline reaction mixture. Then there is the procedure of Dunlap (4), who appears to have based his method upon a suggestion of Winkler (6) that the use of silver oxide under prescribed conditions leads to the preparation of an anhydrous product. The analyst, however, must anticipate his needs well in advance of use and must be satisfied with a product whose water content has been slightly increased, inasmuch as the silver oxide is formed in situ from reagents, one of which is in aqueous solution. This method for making ethyl alcohol aldehydefree, or substantially so, is not necessarily expensive, because the silver can be recovered and little alcohol is lost during purification. This procedure has received recognition in the U. S. Pharmacopeia. Finally, there is the method which is used in the purification of ethyl alcohol for determination of aldehydes in citrus flavoring extracts (2). Chace (3) seems to be responsible for this mode of procedure, which embodies the use of m-phenylenediamine hydrochloride. A 48-hour diges-
tion period of this reagent with the alcohol must precede distillation, the permissible recovery being approximately 85 per cent. I n the second group, or remedial methods, is one which to date seems to have passed unnoticed. It is suggested by Englis and Mills (6),who found that the addition of sodium hydrosulfite to a discolored alcoholic potash solution is effective, although the reaction rate is exceedingly slow. This method is, however, essentially a preventive one, in that the recommended course of procedure is to add the hydrosulfite to the alcoholic alkali solution immediately after it has been prepared. The reaction whereby discoloration is prevented is probably twofold: the inhibition of the photochemical decomposition of alcohol to aldehyde, and the reduction of any aldehyde present per se to alcohol. Fundamentally, however, the analyst does not get away from the necessity of beginning his preparation with a solvent which is substantially free of aldehydes. The method herein proposed, in part suggested by the observations of Englis and Mills, rests upon an application of the fact that nascent hydrogen reduces an aldehyde to its corresponding alcohol at moderate temperatures. This reaction, which is an exothermic one, is brought about by adding to the raw alcohol potassium hydroxide and metallic aluminum, or any metal or alloy yielding hydrogen under these conditions, and digesting the whole for a short time. Zinc may be substituted for the aluminum, but because it is slower to react with alkali than aluminum, its use in the treatment of a product relatively high in aldehyde content will require a longer digestion period. Sodium amalgam may also be used to effect the reduction, but recourse to this reagent hardly seems necessary unless one desires to prepare a product which is both water- and aldehyde-free. Since the alcohol of commerce is relatively low in aldehyde content, a satisfactory degree of reduction will be obtained without a preliminary digestion by the addition of 5 to 10 grams of the metal in granular form and 8 to 10 grams of potassium hydroxide to one liter of alcohol. Ethyl alcohol containing 0.2 per cent added acetaldehyde has been successfully treated by this method by refluxing the reaction mixture for one hour before distillation. The efficiency of the proposed procedure for removing aldehyde from ethyl alcohol was demonstrated by the following experiment, in which *conditions far more drastic than any likely to be met with in actual work were set up. Separate portions of a standard solution of acetaldehyde (17 mg. per cc.) in purified alcohol were treated, respectively, with potassium hydroxide and aluminum, and with alkali only. Both solutions were then subjected to reflux distillation, during the course of which samples were withdrawn from time to time for analysis as to aldehyde content ( I ) .
