INDUSTRIAL AND EiYGINEERIXG CHEMISTRY
July 15, 1930
generated, the bubbles can be counted in E and the speed of the reaction so controlled that only about one bubble per second passes through the tube n i t h a 4 mm. bore. Two bubbles per second is too fast for perfect absorption. As the reaction in A s l o w down, the acid is added faster until all has gone in. Then the stopcock in C is closed and the flask A gently heated, so as to maintain the same rate of flow of gas through E , until the liquid in A boils. Boiling is continued for a minute, and then the flame turned down gradually. .Issoon as the tendency to suck back appears, the stopcock in C is s l o ~ ~opened ly to allow air to enter and replace the gradually condensing water vapor in A . The aspiration of purified air through the apparatus a t the same rate is continued for about an hour after the liquid in A has attained room temperature. The increase in w i g h t of G represents the n-eight of carbon dioxide liberated from the sample taken. The above procedure also holds when hydrochloric and sulfuric acids are used for decomposing the carbonate, and when a Geissler tube containing a 50 per cent solution of potassium hydroxide is substituted for G as the weighed absorption vessel. Precautions, however, must be taken to prevent hydrochloric vapor from reaching the absorption vessel as explained below, and to prevent loss of water from the Geissler by using fresh Dehydrite in the guard tube accompanying it. Sonic of the determinations made with this apparatus are giyen in the accompanying table. Observations
A mass of evidence is a t hand showing that carbonates niay be analyzed by this method with more uniformly accurate results than a n y other tried, and that its simplicity of construction makes i t possible for any one with but a meager
335
knowledge of chemistry to assemble the parts and carry out a determination. K h e n sulfuric acid is used to decompose the carbonate too low results are obtained, but equally good results may be had Tvith hydrochloric and perchloric acids, the former requiring a n extra absorption tube containing anhydrous copper sulfate on pumice to retain the volatilized acid. For this reason perchloric acid is the preferable acid to use in the analysis of this type of carbonates. Carbon Dioxide Determinations
AcCEPTED
WT.
VALUE
OF
SAMPLE
Grams
FOR
ACID
.kBSORBBNT
Con OBTAINED Grum 3';
COz
ERROR e,
N O . 46 ANALYZE ID LIMESTO"E
KOH in Geissler KOH in Geissler KOH in Geissler KOH in Geissler
0.69206 0.69626 0.60986 0.74196 0.72676 0.61086 0.65406 0.72936 0,76276 0,59236 0.71026
HC1 HC1 HC1 HzSOa HClOa HClOa HClOi HClOn HClOa HClOI
KOH in KOH in KOH in KOH in KOH in Ascarite Ascarite
0.8494 1,1499 0,6667 0.8741
HC1 HCl HClOa HClOa
Ascarite Ascarite Ascarite Ascarite
1.0253 1.0497 0,8678 0.4778 0,4512 0.4197 0,5864
HC1
HCI HCl HClOa HClOi HClOa HCIOi
Ascarite
0,7802 0,70435 0,72385 1.2021
HClOa HClOi HClOi
Ascarite Ascarite Ascarite
HClOk
Ascarite
Geissler
Gii&i&
Geissler Geissler Geissler
0,2828 0,2844 0,2479 0.28402 0,2762 0.2495 0.2677 0.2982 0.30832 0.2411 0.28862
40.86 40.84 40.65 38.28 38.00 40.84 40.92 40.87 40.96 40.70 40.63
40.86 40.86 40.86 40.86 40.86 40.86 40.86 40.86 40.86 40.86 40.86
0.00 -0.02 -0.21 -2.5s -2.86 -0.02 +0.06 +0.01 +o. 10 -0.16 -0.23
43.98 44.02 43.78 43.93
43.97 43.97 43.97 43.97
+0.01 +0.05 -0.19 -0.04
29.79 29.79 29.79 29.79 29.79 29.79 29.79
-0.12 -0.05 -0.11 +0.34 +O. 13 0.00 +0.31
PURE I C E L A N D SPAR
0.3736 0.5062 0,2919 0.3840
NO. 48 ANALYZED LIMESTONE
0.3042 0.3122 0 2539 0 1440 0 1350 0 1250 0 1739
Ascarite
Ascarite Ascarite Ascarite Ascarite Ascarite
29.67 29.74 29.68 30 13 29.92 29.79 30.10
DOLOMITE
0.3693 0.33365 0.3407 0.5700
47.33 47.24 47.36 47.24 47.06 47.24 47.41 47.24
f0.09 +0.12 -0.18 +0.17
Aluminum Hot Plate and Dutch Oven' H. V. Churchill and R. W. Bridges ALUMINUMRESEARCHLABORATORIES, NEW KENSINGTON, PA.
TARTIKG with the use of a small aluminum plate, supported on an iron ring stand, there has been a gradual development in the use of aluminum for the construction of hot plates and ovens in the Aluminum Research Laboratories. A t present two pieces of apparatus, the hot plate shown in Figure 1 and the Dutch oven shown in Figure 2, are in use. The Dutch oven is the more recent development. Both pieces of apparatus have given complete satisfaction for the purpose intended. They are constructed of 3s aluminum-manganese alloy, which is somewhat stronger and stiffer than commercially pure aluminum. The heating units used in these laboratories are a Chaddock burner for the hot plate and two small gas burners of the old Bunsen type for the oven. By supplying heat in this way it is possible to evaporate sulfuric acid readily, and mercury slowly, which indicates a temperature of about 300" C. The construction of both types of apparatus is such that they may be used more or less interchangeably as a hot plate or Dutch oven. If desired, the hood of the oven may be remored and the burners moved underneath the plate for direct heating; or very efficient overhead heating may be obtained by plating the evaporating vessel on the lower plate in the body of the hot plate. (Figure 1) This lower plate is adjustable, and may be brought as close to the flame as desired. The interior of the hot plate may also serve as a drg-
S
1
Received April 10, 1930.
ing oven in cases where close control of the temperature is not important, as in drying precipitates previous to ignition. Aluminum possesses the following advantages over iron or steel as a material for use in constructing hot plates and ovens:
R EMOVA6 L E
Figure 1-Hot
Plate
336
d YA L Y TICAL EDI T I O S
REMOVABLE HOODJ
1-01. 2, N o . 3
(4) The appearance of the plate or oven is more attractive. Unsightly corrosion products are not formed by mere exposure to damp air as with iron, and when they result from contact with reagents they are less conspicuous than iron salts.
/m I
GAS BURNERS F i g u r e 2-Dutch
Oven
(1) Aluminum is lighter, and the plate and oven are accordingly more easily moved. A substantially constructed hot plate, with a top 18 by 21 inches, weighs about 26 pounds, exclusive of the burner. This weight is about equally distributed between t h e top plate and body, which are not fastened together. The oven, exclusive of the burners, weighs about 22 pounds, and this is distributed among three parts, none of which weighs over 9 pounds. (2) Aluminum possesses a higher thermal conductivity. (3) The amount of heat required to maintain the aluminum hot plate a t a given temperature is less than that required for steel as aluminum has a low emissivity.
This equipment, as designed, has ample strength to support all loads which it will be called upon to carry. Any tendency of the plate to warp, due to the development of strains in the metal, may be overcome by reversing the plate each day. The aluminum parts used in constructing the hot plate are: 8-11/a X 11/4 X '/4 X 1 3 l / ~inches Lg. 3SH angles 4-11/z X I'/z X '/a X 10 inches Lg. 3SH angles 3-9 X 13'/2 inches X No. 14 Ga. 3SH sheets X 13l/z inches X No. 14 Ga. 3SH sheet 1-8 1-21 X 18 X "8 inch 3SH sheet 1-11 X 13l/2 inches X No. 14 Ga. 3SH sheet, having an opening of 3-inch diameter at its center for the burner 2L'--3/r X 3 / / ~inch ~ Brazier head aluminum rivets For construction of the Dutch oven: 4-11/z X 1'/2 X ' / r X 18 inches Lg. 3SH angles 2-11/t X l ' / t X '/a X 10 inches Lg. 3SH angles 4-11/2 X l l / z X '/4 X 5'/z inches Lg. 3SH angles 1-19'/2 X A11/4 X 3/8 inch 3SH sheet 1-26 X 17 inches X No. 8 Ga. sheet, which can be folded to form the oven top 2-51/& X 1 1 / 8 inches X No. 16 Ga. 3SH sheets, for folding and binding the corners of the oven top 3€1-~/4 X 3//16 inch Brazier head aluminum rivets
Carbon, Hydrogen, and Nitrogen Determinations Using a Metal Tube' S. Avery a n d D. Hayman THE c N I V E R S I T Y
OF NEBRASKA, LINCOLN, N E B R
Copper T u b e with Air-Cooled Ends
HE use of a copper lube with water-jacketed ends has been described by one of the writers ( 1 ) . Since this publication they have devised a similar tube
T
having air-cooled ends. The cut shows the principal feainch (standard) iron pipe size tures. A copper tube, (actual inner diameter 16.8 mm.), is provided with ends made of nickel tubing brazed to the copper. The nickel tubing, being a poor conductor of heat in comparison with copper, partially protects t h e stoppers from burning. The combustion tube thus constructed is telescoped into an outer jacket of nickel of approximately the same length as the copper tube, not including the terminals. This nickel tube also prevents the combustioii tube proper from external oxidation. On the nickel ends of the copper combustion tube (not the protecting jacket) are brazed vanes of copper to act as coolers. These vanes act precisely in the same u a y as the metal vanes used for cooling purposes in internal-combustion engines. I n such a tube the combustion is made in essentially the same way as in the tube cooled with water. I n order to vaporize the water from the combustioii that would otherwise collect a t the entrance of the dehydrite tube during the course of the analysis, heated air is blown against the constricted part of this tube as shown in the cut. T h e Preheater The cut also shows the use of nickel (or monel) tubing of small diameter in the construction of a preheater. The I Received April 30, 1930. Presented before the Division of Organic Chemistry a t the 79th Meeting of the American Chemical Society, Atlanta, Ga., April 7 t o 11, 1930.
copper vanes are brazed to the nickel. The air or oxygen to be freed from carbon or hydrogen contamination is passed slowly through the preheater, which is kept at cherry-red heat by a single fish-tail burner. This preheater is convenient, efficient, and constructed a t a negligible cost. Nickel Tube i n Nitrogen Determinations The nickel tube may be used satisfactorily for determining nitrogen by the Dumas method. I n fact, nickel tubing might well replace copper for carbon determinations except that it is not yet possible to obtain such tubing free from carbon. For total nitrogen determinations the nickel tubing may be provided with copper vanes for air cooling or with waterjacketed ends. Such a tube may be used according to the method given by Fisher ( 2 ) ,or with such modifications of the same as the analyst may care to apply. Difficultly Combustible Volatile Substances Inasmuch as the temperature at which a copper tube may be used is relatively high, tubes of this metal with either airor water-cooled ends may be used to advantage in the analysis of substances forming difficultly combustible, volatile products. I n the case of benzene, hexane, heptane, and similar compounds, the following procedure was found to be satisfactory: A tube to contain the sample for analysis, as shown in the cut, is weighed, 0.12 t o 0.15 gram of liquid is drawn in, the ends of the capillaries are sealed, and the whole is reweighed. One end is now inserted through a rubber stopper into the combustion tube, already heated in the furnace to cherry red, while the other is connected with the air supply. When the tube containing the substance for analysis is in
