Action of Nessler’s Reagent on Amines
before the transmittance was measured. The pH of the finalsolutions was near 12.1.
HERMAN A. LIEBHAFSKY AND LESTER B. BRONK General Electric Company, Schenectady, N. Y.
Figure 1 contains results for ammonium chloride and for CYphenylnaphthylamine. The color of the ammonia compound developed rapidly, and no trace of solid matter vas ever observed in this case. With the amine, the color appeared much more slowly, but eventually became much more intense. Scattering of light by suspended matter is responsible for much of the decrease in transmittance at the longer wave lengths (Figure 1, experiment 9) ; this decrease virtually disappeared when the suspensions were rrntrifuged (Figure 1, experiments 7 and 8). Figure 2 gives results for several other amines. It is clear that diphenylamine resembles a-phenylnaphthylamine in its reaction nith Sessler’s reagent. If this reagent acts on the other amines at all, then-so far as the spectrophotometer can show-it does so to a smaller extent than on ammonia.
HE: authors were recently surprised to discover that Sessler’s Treagent on standing gives a more intense color with a-phenylnaphthylamine than with an equivalent amount of ammonia, a fact apparently not, predictable from the extensive and complex literature on this reagent. The results of several exploratory experiments on this and other amines are accordingly given below. PROCEDURE
An amount of ammonium chloride or of amine roughly equivalent t o 7 micrograms of combined nitrogen was used in all determinations. Known solutions in water or in 95% ethyl alcohol when necessary (aniline, a-phenylnaphthylamine, diphenylamine) were prepared from the laboratory stock except in the case of a-phenylnaphthylamine, which was recrystallized once from alcohol and twice from petroleum ether. Appropriate volumes of these solutions were diluted with 25 ml. of water, whereupon 1 ml. of prepared Xessler’s reagent was added, and the volume adjusted to 27 ml. with water. Transmittance measurements were then made on a recordingspectrophotometer on about 2 ml. of the resulting solution or suspension; the cell thus contained about 0.5 microgram of combined nitrogen. Except when centrifuging was rworted to, any solid that had settled was redispersed by shaking
40
. EXP’T
DISCUSSION
Sichols and Willits (1) concluded after a thorough investigation that the action of Nessler’s reagent on ammonia produces in colloidal suspension a very insoluble compound of empirical formula NH2Hg213. The results reported here for the two secondary aromatic amines seem to be in complete accord with this conclusion. In thr first place, these amines have only one hvdrogen on the
ADDED OFpgR7ml) STANOING (HRS
SUBSTANCE
30
I
100
100 7 8
“
I‘
”
”
I’
1
116
112
100 100
70
.
”
9 100 16 a. CENTRIFUGED BEFORE TRANSMISSION WAS MEASURED
0
I NOTE.
I
CURVES FOR FIRST IIIEXPERIMENTS L I E WITHIN RdGlON INDlCATEd
Figure 2. Transmittance Measurements on Amines Combined with Nessler’s Reagent
588
V O L U M E 20, N O . 6, J U N E 1 9 4 8
589 ACKNOWLEDGMENT
nitrogen atom, so that they could form compounds of the type S H Z H ~ Zbut I ~ , not of SOme of the m ~ speculative e types that have been suggested as the nesslerization products of ammonia. In the second place, the aromatic radicals in these two amines Yhould rend to make their nesslerization produrts insoluble in 11-ater. The interaction of amines with Nessler's reagent obviously affords material for several interesting investigations.
The authors wish to thank Murray AI. Sprung for helping and advising them. LITERATURE CITED
(1) Nichols, M. L., and Willits, C. O., J. Am. Chem. SOC.,56, 769 (1934) ; contains an extensive bibliography. RECEIVED October 3, 1547.
Apparatus for Absorption of Carbon Dioxide in Mass Spectrometric Determination of the Carbon Isotopes KALERVO RANKAMA, Department of Geology, University of Chicago AND
'
K. J. NEUVONEN, Institute of Geology, University of Helsinki, Finland
S 1946 tht. authors carried out a series of combustions of car-
bonaceous materials from the Pre-Cambrian rocks of East Fennoscandia with the ultimate aim of obtaining material for mass spectrometric determination of the abundance ratio, Clz/C13, of the carbon isotopes, the results of which work will be published elsewhere. One of the central problems of the investigation consisted of the development of a suitable combustion method and apparatus for converting the carbon into barium carbonate without the addition of carbon compounds from extraneous sources during the stages of the work. An apparatus -ras finally constructed for the purpose, and a short description of i t is given below. APPARATUS
2
PROCEDURE
Prior to the combustion, all air is expelled from the system by passing a current of oxygen through it for half an hour a t a speed of 50 ml. per minute. The speed is then increased to 80 ml. per minute and part of the oxygen is drawn through the lower fritted funnel by connecting the latter with vacuum (15 minutes). For the next 20 minutes another part of the oxygen is forced through the upper fritted funnel by connecting the T-tube above the atomizer with vacuum. The flow is then adjusted to 20 ml. per minute, 100 ml. of barium hydroxide solution are pumped through the upper funnel into the absorption bulb, and the flow is regulated to 10 ml. per minute. The charge in a platinum boat is heated cautiously over a small flame of a Bunsen burner and the combustion is allowed to proceed until about one half of the sample has been consumed, after which the flame is removed. The filter pump is started, the upper filter funnel is washed with a few milliliters of water, and 20 ml. of water are pumped into the absorption bulb. The flow of oxygen is adjusted to 5 ml. per minute, and the precipitated barium carbonate is filtered through the fritted filtering tube in 3 to 20 hours, depending on amount of the precipitate. Sext, 120 ml. of water are pumped into the absorption bulb and passed through the loner funnel, connected with vacuum. The filtration will take from 5 to 25 hours. The precipitate is washed with a few drops of water and the combustion continues to completion. The flow of oxygen through the drying tube attached ' to the side tube of the absorption jar is cut off, and the carbon dioxide-bearing oxygen is allowed to pass through the barium carbonate precipitate for 20 minutes. This is done in order to convert the barium hydroxide present in the precipitate into barium carbonate. The gas mixture is then alloned to pass through the upper fritted funnel for a few minutes, the precipitated barium carbonate is washed six or eight times with 2 to 3 ml. of water, and the oxygen-carbon dioxide mixture is once more allowed to pass through the precipitate. In 30 minutes the precipitate v.31 become dry, and is placed in a drying cabinet and dried a t 200" C. for 2 hours. Finally, the precipitate is transferred into a small glass tube which is heated for a moment over a n asbestos board a t approximately 600" C. and sealed.
3
cylinder containing oxygen was connected with a pressure regulator to maintain a constant delivery pressure. The oxygen was washed with 40% sodium hydroxide solution in a gas-washing bottle, and allowed to pass another pressure regulator and a bubble counter. .Ifter passing a U-shaped absorption tube filledwith calcium chloride and Ascarite, the gas entered a semimicro combustion tube placed in a combustion furnace. The latter half of the combustion tube was filled with cupric oxide. i%
The whole apparatus centers around the absorption assemhly, which is presented in Figure 1. An absorption bulb with side tubes for its connection with the combustion tube and \\itha small straight drying tube is filled with calcium chloride and Ascarite. To the upper end is sealed a fritted funnel of fine porosity (3G4, Schott & Genossen) and of 30-ml. capacity, and the lower end is provided, through a ground-glass joint, with a fritted micro filtering tube (12G3) of 2-ml. capacity and of medium porosity. The filtering tube is connected with a filter pump through a rubber stopper and a filtering flask. The upper funnel is equipped with a rubber stopper and con-
nected through it with two flasks, one of which contains saturated barium hydroxide solution and the other pure distilled water, such as that used for conductivity measurements. The flasks have air inlet tubes sealed with small calcium chloride-Ascarite drying tubes. The flow of water and barium hydroxide solution is regulated by means of pinchcocks attached to rubber tubing. The rubber stopper is provided with glass and rubber tubings connected with a rubber bulb (atomizer). The rubber tubing has an interlying T-shaped glass tube to connect it with the filter pump. A small calcium chloride-Ascarite drying tube is also attached. A fourth piece of glass tubing, starting just above the fritted disk, serves as an exhaust for the funnel washings. ToTmrd its lower end the tube is provided with a pinchcock.
12G3
7 Figure 1. Absorption Assembly
During the combustion procedure the usual precaution of glass against glass in all joints TTas strictly observed. A series of preliminary combustions \vas carried out to ensure correct practice in all details. Blanks run with the apparatus failed to produce any barium carbonate precipitate, and it was concluded that the oxygen used in the combustion was of sufficient purity. By means of this apparatus the authors carried out combustions of a series of graphites described above. In many cases this
