ANALYTICAL EDZ TIOS
334
in certain industries where particle size of impurities is liable to be of importance. For example, a soap manufacturer might allow 0.1 per cent of dirt, provided none of it had a particle size greater than 50 microns. Applications of Method The outlined method is quite flexible and is capable of application in many other ways. It is not limited to a n examination of the dirt in gums and resins; the dirt in many other materials, such as glue, gelatin, etc., can be determined by i t with equal ease. Higher magnifications can be used for smaller particles.
T'ol. 2 , s o . 3
Dirt in the material might be allowed to settle for a definite length of time before photographing, and thus allow analysis for just the dirt above a certain particle size by obtaining it in a single plane. If all photographs are taken under constant conditions, including the same exposure time, a good idea of the transparency and color of the material may be obtained from the density of the negative. If a comparison microscope is a t hand, the sample under observation may be compared directly with a standard or another saniple of the same material. "le-The discussion of results applies only t o t h e original photographs I t should be remembered t h a t the originals have su5ered somewhat both in making the composite pictures and also in reproduction of same.
Method for Determining Carbon Dioxide in Carbonates' C. A. Jacobson a n d J o h n W. Haught WEST VIRGINIA UNIVERSITY, ~ I O R G A K TW OW . V.4. N,
OR many years it has been the prkilege of one of the
F
vriters to test a number of the most highly reconimended methods for determining carbon dioxide in carbonates and to evaluate their merits. This was accomplished in connection with a course in advanced quantitative analysis a t the K e s t Virginia Uaiversity. I n order to ascertain the degree of success the average student would have in analyzing a limestone or dolomite by a given method, the same sample was submitted to groups of students to be analyzed by different methods. Upon checking over the results it was concluded that a modificationmight be made so that better and more uniform results lvould be obtained by the analyst who is not an expert in this field.
A p p a r a t u s for D e t e r m i n i n g C a r b o n Dioxide i n C a r b o n a t e s
an inch from the bottom of the flask. The separatory funnel is in turn fitted 11 ith a glass-stoppered absorption tube, C, containing Ascarite provided t o remove carbon dioxide from the aspirated air after the reaction is over. The condenser is made by cutting off the closed ends of t n o sniall bideneck test tubes and fitting the cut ends together nith a piece of rubber tubing. Tube E serves the dual purpose of absorbing most of the moisture from the carbon dioxide and permitting the regulation of the flow of gas through the apparatus. The U-tube F is filled with Dehydrite for the purpose of taking out the last traces of water. The lon-er compartment of the Fleming absorption tube, G, is filled with Ascarite and the upper compartment with Dehydrite, which serves to retain any moisture that niay he formed in the Ascarite bulb during the carbon dioxide absorption. G should be of such a size that its weight when filled shall not exceed 100 grams. The upper end of the Fleming bulb is connected with the suction tube, H , connected either with a filter pump or a n aspirating bottle by mean5 of a glass stopcock inserted between G and H for the purpose of regulating suction. Procedure Before the determination is started the apparatus is carefully tested for leaks by applying suction a t H . -4bubbler (not shown) is inserted between G and H for this test and then removed. Leaks are seldom encountered, however, if the glass-stoppered joints have been previously tested. All rubber connections are made by heavy wall pure gum tubing. The rubber stoppers used are small, which more readily permit of making tight joints. Having proved the apparatus tight, about 3 to 4 cc. of water are added to the samplr (about 0.7 gram) through B, after which about
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
