Paddle stirrer

Cold water Hot water Lead 0.40 r.p.m. paddle stirrer 90-360... 

The stirrer used is a bent glass rod which nearly scrapes the sides of the flask. A simple paddle stirrer is not efficient enough to stir the semi-solid mass. 

The usual type of glass paddle stirrer is also widely used in conjunction with an electric motor fitted with either a transformer-type, or a solid-state, speed controller. The stirrer may be either connected directly to the motor shaft or to a spindle actuated by a gear box which forms an integral part of the motor housing by these means, wide variation in stirrer speed can be achieved. 

The electrodes are made of platinum gauze as the open construction assists the circulation of the solution. It is possible to use one of the electrodes as stirrer for the solution, but special arrangements must then be made for connection of the electrolysis current to this electrode, and an independent glass-paddle stirrer or a magnetic stirrer offer a simple altemative.Typical electrodes are the Fischer type depicted in Fig. 12.4 a glass tube is slid into... 

The kind of stirrer is not important. The submitters obtained similar results with a three-blade propeller -turning at 600 r.p.m. and a paddle stirrer turning at 78 r.p.m. They believe that a rocking autoclave could be substituted for a stirred one. 

Stirring. Stirring of the reagents will not interfere with cavitation and may prove necessary for acceptable reaction rates. Solids must not be allowed to collect on the bottom of the flask. If the solid loading is high and cavitation cannot suspend all of it, a paddle stirrer should be used. 

For this purpose, 500 ml of a 140 mg/1 kaolin suspension was treated with an amount of polymer A corresponding to 0.5% of the clay concentration (i.e. the optimum dose). After 15 seconds of rapid mixing, the suspension was subjected to slow (30 r.p.m.) stirring, using a paddle stirrer. Samples were withdrawn at different intervals directly into the syringe and a filtrability determination was carried out. 

B. 1-Amino-l-methylcyclohexane. A 3-1. three-necked flask is fitted with a paddle stirrer, a condenser, a thermometer, and a... 

Devulcanization of Rubber Peelings. Rubber peelings (10 g)(8) were charged into a 3-neck, 250 mL flask fitted with a water-cooled condenser and paddle stirrer. A solution of catalyst in 50 mL of... 

A 2-1. fouir-necked flask equipped with a sealed, Teflon-paddle stirrer, a merrcury thermometer, a gas inlet tube, and a dropping funnel is charged with 1.21. of anhydrous tetrahydrofuran (Note 1) and 50 g. (7.1-g. atoms) of lithium pieces (Note 2) under an atmosphere of prepurified nitrogen. The stirred mixture is cooled to —20° by means of a dry ice-acetone bath and a mixture of 100 g. (1.00 mole) of methyl methacrylate (Note 3), and 411 g. (3.0 moles) f n-butyl bromide (Note 4) is added dropwise over a period off 3-4 hours. During this addition, an exothermic reaction ensues which is controlled at —20° (Note 5), and on completion of the addition, the vessel is maintained at this temperature, with stirring, for an additional 30 minutes. The contents oF the flask are then liltered with suction through a... 

Dispersion system 1 g of low-molecular-weight poly(vinyl alcohol) which serves both as dispersing agent and protective colloid, is dissolved in about 150 ml of distilled water in a narrow 600 ml beaker. It is stirred with a paddle stirrer at room temperature for about 2 h until dissolved.The polymer used should be a partially (88%) hydrolyzed poly(vinyl acetate), a 4% aqueous solution of which has a viscosity of 4 cP. 

The amine solution (4) is now immediately run in dropwise over a period of 30 s and the stirrer speed reduced to 2000 rpm After 2-3 min the high-speed stirrer is replaced by a normal paddle stirrer and the dispersion stirred (500 rpm) for a further 30 min at room temperature to complete the interfacial polycondensation between terephthaloyl dichloride and diethylenetriamine. 

Case 1 Data on heat transfer between liquid and the vessel wall and between liquid and the surface of helical coil in the vessels stirred with flat-blade paddle stirrers were correlated as [4] ... 

Anhyd HF (ca. 20 mol) was added slowly to the purified aromatic amine (1 mol) contained in a 1-L, 2-necked Monel metal flask cooled in ice. The solution was stirred at 0 C by means of a stainless steel paddle stirrer while dried, reagent grade NaNOz (82.8 g, 1.2 mol) was added in small portions over a period of 1 h. The flask was then connected to an ice-cooled copper reflux coil and the mixture was warmed... 

In a 3-1. round-bottomed flask fitted with a small glass paddle stirrer and a reflux condenser are placed 101 g. (0.4 mole) of /3-methyl-/3-phenyl-a,a,-dicyanoglutarimide,2 and a mixture of 500 ml. of water, 500 . of concentrated sulfuric acid, and 400 ml. of glacial acetic acid. Without starting the stirrer (Note 1), the mixture is heated under reflux for 2 hours. Then the stirrer is cautiously started, and reflux is continued for a total of 80 hours. The reaction mixture is transferred to a 6-1. Krlenmeyer llask, 3 1. 

Vigorous stirring is necessary in order to prevent the zinc dust from caking on the bottom of the crock. The submitters employed two mechanically driven stirrers in order to keep the zinc dust in suspension. The checkers used a single paddle stirrer successfully. 

P,5a-Dihydroxyandrostane-6, l-dione 3-Acetate (76)53a The foregoing mixture of epoxides (75) (18 g) is dissolved in 180 ml of hot, reagent-grade methyl ethyl ketone. The solution is cooled to room temperature and the crystalline mass is stirred with a paddle stirrer while 18 ml of a solution prepared from 15 g of chromium trioxide in 20 ml of water is added in portions over a period of about 10 min. During this time the temperature rises to about 58°. After an additional 10 min, 1 liter of water is added with stirring... 

B. 13-Isovalerolactam. A 200-ml. beaker is provided with a combination pH electrode, a mechanically driven paddle stirrer, a thermometer, and a syringe or dropping funnel (Note 9). An amount of water just sufficient for immersion of the pH electrode (20 ml.) is introduced, and with vigorous stirring the first portion... 

Two hundred seventy milliliters (497 g., 4.86 moles) of 96% sulfuric acid (Note 1) is poured into a 1-1. three-necked flask equipped with a paddle stirrer driven by a powerful motor, a dropping funnel with a gas by-pass, and a thermometer that dips into the acid. The reaction mixture is stirred vigorously (Note 2) and maintained at 15-20° by means of a cooling bath as 3 ml. of 98-100% formic acid (Note 3) is added dropwise. Under the same conditions, a solution of 28.5 g. (0.25 mole) of 2-methyl-cyclohexanol (Note 4) in 46 g. (1.00 mole) of 98-100% formic acid is added in the course of 1 hour. The reaction mixture foams during the additions. The mixture, which is a very light cream color, is stirred for 1 hour at 15-20° and then is poured with stirring onto 1 kg. of crushed ice in a 4-1. beaker. The carboxylic acid separates as a white solid. 

A 1-1. three-necked round-bottomed flask is fitted with a Tru-bore paddle stirrer, a long water-cooled reflux condenser, a dropping funnel, and a gas inlet as shown in Fig. 11. The apparatus is dried by flaming with a Bunsen burner while being flushed with a stream of dry nitrogen. 

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