Closing tubes with stoppers

Checking the Clamp. Fill the siphon with water. It must contain no air bubbles. To do this, take the test tube off stopper 1, open clamp 3, blow air through the tube with stopper 1, and close the clamp again. See if any water flows out of the siphon tube. 

Compounds of Vanadium in Lower Oxidation States. Melt paraffin in a porcelain bowl or test tube. Put seven test tubes with stoppers onto a test tube stand. Pour 10 ml of a sodium vanadate solution into a small 50-ml flask, add 10 ml of a 20% sulphuric acid solution, and put in 8-10 small pieces of granulated zinc. Watch how the solution s colour changes. As a new colour appears, pour off 1-2 ml of the solution into each of three of the tubes. In one of them, pour melted paraffin over each layer of liquid with a new colour. Close the other two tubes with their stoppers and pour the following portion of the solution with a new colour into two empty tubes with stoppers. 

Solidification Point — shall not be less than 73.0° when deed in the same type of apparatus as shown in this Vol under Diphenylphthalate. Melt a 50g sample in a covered 250ml beaker by immersing its lower half in a water bath at 90 to 95° for 15 mins, and transfer the liquid to the tube C (See Fig on p D1473) filling it to within ca 1.5 inches of the top. Close the tube with stopper (a), provided with standard thermometer T, correction thermometer Tj and stirring rod R. Immerse the stoppered rube in a water bath at 85—90° for 5 mins, wipe it off and place inside tube B, which is, in turn, placed inside 1 liter jar A. Proceed now exactly as descrihed under Diphenylphthalate... 

POUR A FEW ml HOUSEHOLD OIL IN TEST TUBE. PLACE WAD OF STEEL WOOL NEAR MOUTH OF TUBE. CLOSE IT WITH STOPPER THAT HAS A GLASS TUBE WITH JET TIP. HEAT STEEL WOOL. A LITTLE LATER, ALSO HEAT THE OIL. OIL IS CRACKED INTO GAS THAT BURNS WHEN IGNITED. 

F) Benzoylation of an Amine. (See also page 175.) Place 10 ml of 10 per cent sodium hydroxide solution in an eight-inch test tube, and add 2 ml of o-toluidine. Close tube with a No. 5 or No. 6 solid rubber stopper and shake for a few seconds. Remove the stopper and add 2 ml of benzoyl chloride. Shake vigorously for 1 to 2 minutes, then at intervals for 8 to 10 minutes. Pour the mixture into water. The benzoyl-o-toluidide separates out. Filter, and wash the crystals with water. Recrystallize from alcohol. The yield is 3-4 g. The melting point may be determined in the usual way. 

A) Preparation of Benzalacetophenone (Sm.). Place in an eight-inch tube a solution of 1 g of sodium hydroxide in 8 ml of water and 6 ml of alcohol. Cool in an ice-salt mixture. Add 2.6 g of acetophenone (2.6 ml) shake well, and immerse again in the cold bath. Add 2.3 g (2.2 ml) of freshly distilled pure benzaldehyde, close tube with a solid rubber stopper, and shake vigorously. Allow... 

Round-bottomed flasks (Fig. 22(A)) of various sizes and having necksof various lengths and widths. They can be closed with stoppers (Fig. 22(B)), or fitted with any of the following units reflux air-condensers (Fig. 22(C)) or water condensers (Fig. 22(D)) distillation heads, of the simple knee-tube type (Fig. 22(E)), or with a vertical joint (Fig. 22(F)) for thermometers, etc., or with... 

Fig. 4. Schematic of the Closed Container Sampling technique used in the Baxter PARAMAX analy2er showing (a) the collection tube with bar-coded label being brought into sampling position under the caimula (b) the tube raised so that the caimula has penetrated the stopper (c) the sample sensing probe coming through the caimula to aspirate the exact volume required for each assay and (d) after sampling, where the tube is lowered away from the cannula.

Labb recommends a slight modiflcation of the above process, by which he claims that the separation of crystals at the junction between the unabsorbed oil and the sulphite liquor is prevented, and greater accuracy in reading off the. percentage therefore attained. He employs a stoppered bulb, prolonged at the bottom into a graduated cylindrical closed tube, and into this are introduced 5 c.c. of the oil, together with... 

A 2-1. three-necked round-bottomed flask is fitted with a reflux condenser and a glass inlet tube connected to a cylinder of nitrogen. The third opening of the flask is closed by a stopper. The top of the condenser is connected to an air trap which consists of two SOO-cc. suction flasks joined in series. The first suction flask is empty the second contains 100 cc. of paraffin oil, and the inlet tube of this flask extends slightly below the surface of the oil. 

Now fit the calcium chloride tube closely to the constricted part of the combustion tube and connect the sodium hydroxide-asbestos tube to the calcium chloride tube of the aspirator. Then remove the rubber stopper from the combustion tube, push back the stand carrying the drying apparatus so as to make more room, raise the copper block with the boat to the opening of the combustion tube, with the forceps insert the boat, push it inwards 4-5 cm. up to the furnace with a clean glass rod of suitable size, taking care not to tip the boat over, insert the rubber stopper loosely into the tube, moistening the stopper if necessary with a very thin film of glycerol,... 

For the determination, weigh in a platinum boat, in the usual way, 20-30 mg. of substance and insert the boat into the tube. The boat should rest 6-7 cm. beyond the long roll of wire gauze. Now close the tube with a rubber stopper and a capillary tube drawn out to a fine point and connect to an oxygen gas holder. Between the gas holder and the capillary interpose a small bubble-counter containing 50 per cent potassium hydroxide solution. 

To about 15 mg in a test-tube, add 3 drops of phosphoric acid and close the tube with a stopper through which passes a smaller test-tube filled with water, and on the outside of which hangs a drop of lanthanum nitrate solution. Heat in a water-bath for 5 minutes (or if necessary bring slowly to the boil over a flame). Mix the drop of lanthanum nitrate solution with 1 drop of 0.02 N iodine on a white tile, and place 1 drop of dilute ammonia solution at the edge of the mixture. A blue color slowly appears at the junction of the two liquids indicating the presence of an acetyl group. 

A convenient laboratory-scale storage device consists of a Schlenk tube (about 100 raL) with a Teflon valve in the side arm and a socket joint on top of the body of the tube. The stopper is the corresponding Teflon-seated ball joint attached to a small Teflon valve (Fig. 2), which allows the air in the space above the socket to be purged with nitrogen prior to closing the tube. The ball and socket joint is preferable to the common cone and socket arrangement because the metal oxide crust that invariably forms in the joint is more easily broken. 

By means of a graduated pipette provided with a rubber suction bulb, transfer 2ml of MG to a La Motte Co comparator tube and add neutral water to the mark on (he tube. After this, add 0.5ml of La Motte Co bromthymol indicator, close the comparator tube with a clean cork stopper and shake... 

A bottle containing a soln. of 286 4 grms. of decahydrated sodinm carbonate dissolved in twice its weight of water is closed by a stopper fitted with a tube-funnel drawn to a very... 

Extract the hottle filled with water and close it with the stopper containing the tube also filled with water. Thoroughly wipe the entire setup and weigh it. Determine the mass of the water filling the... 

Action of an Acid on a Metal. Assemble the setup shown in Fig. 42. Put 8-10 pieces of granulated zinc in the test tube, pour in 5 ml of a 20% sulphuric acid solution and close the tube with a stopper provided with a gas-discharge tube with its end drawn out upward. Check the purity of the hydrogen evolving. 

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