Cold-forming taps

Taps having no flutes, known as cold-forming taps, produce the thread hy plastic deformation of the material and therefore no swarf is produced hy the action. This type of tap is used with ductile materials such as soft steels, aluminium and zinc alloys. Because the material is displaced, the tapping drill Is larger than that for taps which cut, e.g. an MIO cut thread has a tapping drill of 8.5mm, while an MIO cold-formed thread has a tapping drill of 9.3 mm. 

The loss of large quantities of acetaldehyde is avoided by use of a spiral condenser, with sufficient heating so that a vapor lock is formed—the entrapped liquid should fill about two-thirds of the spiral. In cold weather, the tap water is usually cold enough so that any efficient long condenser, or two in series, is sufficient. 

Experiment.—About 0-5 c.c. of ethyl acetoacetate is dissolved with shaking in the necessary amount of water, a few drops of ferric chloride solution are added, and to the cold solution dilute (1 10) bromine water is added, drop by drop, but rather quickly from a tap funnel, until the red colour of the ferric enolate has disappeared. The enol has now been completely used up by the bromine, but since, in order to restore the equilibrium, more enol is formed, the colour reappears after a short time and can at once be destroyed again by the addition of a few drops of bromine. The procedure can be repeated until the whole of the ethyl acetoacetate is converted into ethyl bromoacetoacetate. By means of this experiment the keto-... 

The cooler is made of galvanized iron, or, still better, of tinned copper and in order to accommodate the long joints of the worm which is soldered to it, its form is oval. The pipe through which it receives cold water is close to the side, and extends nearly to the bottom, as shown at s. Aconnection with the hydrant is made by a branch-pipe and tap, as shown at m. The opening for the exit of the warm wateT is seen at /, and leads into another pipe, ft, running down the outside of the cooler into the drain or gutter. A tap, x, serves for draining off sediment, as it accumulates by deposition from the water. 

Reactors with Field tubes should as a rule have a small diameter (400 mm), because a Field tube ensures that the heat is efficiently withdrawn from the whole surface of the apparatus only if the size is small. The Field tube is situated axially in the fluidised layer of contact mass and longitudinally selects the layer from top to bottom. There is cold tap water circulating in the tube (river water can not be tolerated, because it forms scale deposits in the tube and reduces the heat transfer coefficient). 

Prepare a very concentrated cold solution of sodium stan-nite Dissolve 1 gram of stannous chloride in 1 ce. of water. Dissolve a small lump of sodium hydroxide in its own weight of water, and add this solution, a drop at a time, to the first solution — cooling all the while under the water tap — until the precipitate at first formed redissolves. Then heat the solution. Compare the action with that in Experiment 4. 

Procedure Place 194 grams (6.8 oz.) of 98% sulfuric acid into a beaker, and then place the beaker in an ice bath and cool to 0 Celsius. When the sulfuric acid reaches a temperature of 0 Celsius, slowly add in portions, 100 grams (3.5 oz.) of potassium nitrate or 84 grams (3 oz.) of sodium nitrate over a period of 1 hour while stirring the sulfuric acid and maintaining its temperature at 0 Celsius. After the addition of the potassium or sodium nitrate, slowly add over a period of one hour, 260 milliliters (8.8 fluid oz.) of cold tap water while continuously stirring the sulfuric acid mixture and maintaining its temperature at 0 Celsius (note a precipitate may form before or after the addition of the water. If this is happens, never mind it). Then remove the ice bath and then extract the acid mixture with seven 150-milliliter portions (seven 5.07 fluid oz. portions) of methylene chloride. Afterwards, combine all seven portions of methylene chloride (if not already done so), and then add 7 milliliters (0.23 fluid oz. or 1.4 tsp) of water to the methylene chloride. Then place the entire methylene chloride (two phase) mixture into a distillation apparatus (see the illustration in method 3 below), and carefully distill at 40 Celsius until no more methylene chloride is collected in the receiver flask. 

In a 2-1. round-bottomed flask equipped with a mechanical stirrer are placed 11. of 2 per cent sulfuric acid, 0.5 g. of vanadium pentoxide (Note i), no g. (i mole) of hydroqiunone, and 60 g. (0.56 mole) of sodium chlorate. The mixture is vigorously stirred for about three hours, when the green quinhydrone first formed is converted to yellow quinone. The temperature of the reaction mixture rises to about 40° (Note 2). The reaction is usually complete in three and one-half to four hours. The flask is then disconnected and cooled under the tap, the mixture is filtered with suction, and the quinone is washed once with about 100 cc. of cold water. After drying in a desiccator over calcium chloride, the product weighs 86-90 g. and melts at 110-112°. This material is pure enough for most purposes. Extraction of the filtrate and washings with four loo-cc. portions of benzene yields a further 12-14 g- of quinone, and brings the total amount to gg-104 g. (92-96 per cent of the theoretical yield) (Note 3). 

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