2021
V O L U M E 2 7 , NO. 1 2 , D E C E M B E R 1 9 5 5 Adapter for Suction Filtration Directly into a Volumetric Flask Leonard Ginsburg and Louis Gordon, Department of Chemistry, Syracuse University, Syracuse 10, N. Y. \T PRECIPITATIOX
reactions i t is often desirable to transfer a
1.filtrate, or the dissolution products of a precipitate, directly
from a filtering crucible into a volumetric flask. The adapter indicated as .4 in Figure 1 facilitates such operations. Three w r h adapters f i t t e d 111th T m a l e joints, sizes 10/18, 14/20, and 19/38, will suffice for stoppered v o l u m e t r i c f l a s k s of A 500-nil. or less capacity. These filtering devices 12 CM.
T
have been used in this laboratory with water a s p i r a t o r s for over a year without any implosion of either Pyrex or Exax brand volumetric flasks. However, a safety guard around the 500-ml. flask mav be used in the interest of safety. Thin-walled flasks should not be used unless testa indicate their applicability.
Zimmerman ( 4 ) described an apparatus for the combustion of materials whose vapors might form explosive mixtures with oxygen or air; his combustion tube and method are designed primarily for solids and would probably produce flashbacks and dangerous explosions if used with silanic gases. The apparatus described belon. enables one to mix successive small port,ions of the gas sample n-ith a large excess of oxygen and to burn it without uncontrolled explosions, n-hich might rupture the combustion tube. APPARATUS
The combustion apparatus is similar to t,hat used for standard semimicrocombustions ( 2 , 3 ) , except that the combustion tube is of clear vitreous silica, 10.5 mm. in outside diameter, 8.5 mm. in inside diameter, and 30 cm. long, n-ith a side arm and threeway stopcock as shown in the sketch. The tube is packed with ignited asbestos, platinum gauze, platinum cat,alyet, copper oxide catalyst, silver catalyst, silver gauze, and ignited asbestos. The silver-copper oxide can he heated by means of a Fischer microcombustion furnace (Catalog S o . 20-286-1) and the temperature of this section should be maintained between 550" and 650" C. The platinum section of the train can be wrapped with nickelchromium alloy micro gauze and heated x i t h fishtail burners to a temperature betn-een 850" and 1000" C. The three-way stopcock on the side arm should be protected from radiated heat with an asbestos shield; a jet of air blowing on the glass surface close to the joint serves to dissipate conducted heat away from the ground-glass joint. A Kiederl gasometer (available from scientific apparatus supply companies) is used t'o hold the gas sample.
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Determination of Carbon and Hydrogen in Spontaneously Flammable Gases Howard B. Bradley, Laboratory of Linde Air Products Co., A Division of: Union Carbide and Carbon Corp., Tonawanda, N. Y.
REAGEhTS
COFPEROXIDE CATALYST.Dissolve 60 grams of copper nitrate in about 200 ml. of distilled water in a porcelain evaporating dish. Add 100 grams of iiloxite (Carborundum Co. brand aluminum oxide cylindrical pellets, 3 / , s X 3/18 inch) and evacuate under a bell jar; this draws the air out of the pores of the pellets. When bubbles no longer erupt from the pellets, release the vacuum; the copper nitrate solution now rushes into the evacuated pores. Digest on a hot plate for one-half hour. Decant off excess liquid and dump pellets onto a wire gauze. Heat until dry, using a direct gas flame. Finally ignite in a muffle furnace a t 800" C. for 1 hour.
ASBESTOS
to determine carbon and hydrogen in silane-containing gas mixtures with conventional apparatus have frequently led to explosions or to low results. The mass spectrometer is probably adequate for analyzing most of these mixtures, b u t frequently a determination of total carbon and hydrogen is also desired. A method is described below for carrying out these determinations by a combustion technique on any gas mixtures in which there is danger of explosion. In some cases, silane-containing gas mixtures can be analyzed in a standard Orsat. Ths silane reacts with the potassium hydroxide in the first pipet, liberating its hydrogen and leaving the silicon behind as soluble potassium silicate; the increase in volume is equal to three times the volume of silane in the original mixture. Hydrogen and hydrocarbons can then be burned in the Orsat combustion tubes in the usual way. However, the total carbon and hydrogen of some gas mixtures, such as those containing alkyl-suhstit,uted silanes, cannot be determined in an Orsat. In the caw of ethy! silane, for example, the pot.assium hydroxide in thr first pipet liberates the hydrogen which is bonded to the silicon, but retains the rest of the molecule without breaking the silicon-carbon bond; the ethyl group thus escapes detec tion. Brunn and Faulconcr ( I ) have described an apparatus for the combustion of highly volatile materials and for flammable liquids, in which oxygen is mixed with the combustible vapors before entering the ignition zone. As mixtures of silane and oxygen may explode spontaneously, this apparatus should not be used for this problem.
A
TTENPTS
,k GAUZE
Fr
GAUZE
ASEESTOS
HERE
PLITIN-\IC ~ T A L Y S T Dissolve . 5 grams of platinum chloride in about 7 5 ml. of distilled water and transfer to a 300-ml. porcelain evaporating dish. Add 100 grams of dloxite pellets and complete the preparation as ith the copper oxide catalyst. SILVERCIT.II.YRT. Prepare similarly to the platinum and copper pellet:, using 40 grams of silver nitrate and about 80 grams of Aloxite pellets. Silver gauze, 100-mesh pure silver gauze. Platinum gauze, 100-mesh platinum gauze PROCEDURE
Collect about 20 ml. of the gas to be analyzed in the Kiederl gasometer and dilute m-ith 40 to 50 ml. of argon. As the gasometer is calibrated, it is easy to determine how much of the gas mixture is burned. Connect the gasometer t c the three-my stopcock on the combustion tube. Purge the train with oxygen in the customary way for 1 hour with the Tyater and carbon dioxide absorbers attached. Weigh absorbers and very gently bleed the gas sample into the train.
