Organic vapours

The deposition of organic films by plasma polymerization is an important application of non-thennal plasmas 1301. Plasma polymers are fonned at the electrodes and the walls of electrical discharges containing organic vapours. Oily products, soft soluble films as well as hard brittle deposits and powders are fonned. The properties of plasma... 

For an actual determination, first place in J some stable liquid the boiling-point of which is at least 50 above that of the organic liquid the pour density of which is to be measured. This difference in boiling-point is important, because it is essential that the organic liquid, when nbsequently dropped into the bottom of T, should volatilise rapidly nd so push out an equivalent volume of air before the organic vapour can diffuse up the tube T and possibly condense in the cooler ttppcr portion of the tube. Suitable liquids for use in the jacket are ter, chlorobenzene (132°), rym-tetrachloro-ethane (147 ), P ... 

A flask is provided with a long side neck (Fig. II, 25, 1) through which a capillary is inserted and attached externally by a short length of rubber pressure tubing. With this type of connexion there is essentially no contact of hot vapours with the rubber and little or no contamination results. The neck of the flask is preferably fitted with a standard ground joint if attack of the organic vapours on the rubber stopper is likely to occur. 

No corks or rubber stoppers are, in general, required. Contamination or discolouration due to these is therefore avoided. Occasionally, a small rubber stopper may be employed, e.g., for the insertion of a thermometer, but, should the very small surface of rubber thus exposed to the action of the organic vapours be undesirable, a thermometer with a ground glass cone can be used. 

Fig. II, 56, 6 is a simple distillation head when this is fitted into a flask with a ground glass socket, the assembly is virtually a distillation flask. The bottom cone is usually 19, 24 or 29 the side cone is generafly B19 but may be 24 the thermometer socket is 14. For many purposes, a thermometer is fitted into a one-hole rubber stopper of correct taper and then inserted into the 14 socket the area of rubber which is exposed to the action of the organic vapour is relatively so small that the amount of contamination thus introduced is negligible. If, however, all rubber stoppers must be absent because of the highly corrosive character of the vapour, a thermometer with a 14 cone is employed. It is important to have the thermometer of the same glass as the distillation head, otherwise difficulties may arise owing to the different expansion coefficients of the two kinds of glass.

Fig. 4.1 Adsorption isotherms of some organic vapours on ammonium phosphomolybdate outgassed at 180°C. The isotherm temperatures (reading downwards) were 25°C, 25°C, 25°C, 0°C.

Chromasorb Hydrocarbons, high molecular-weight organic vapours, chlorinated organic compounds... 

Table 10.16 Chromatographic column guide for Century organic vapour analyser...

Century organic vapour analysers are factory calibrated to measure total organic vapours according to a standard (methane). Since different organic vapours interact with the flame ionization detector (FID) to varying extents, it is vital that the instrument user be aware of the magnitude of the variation in order to obtain the most accurate data. Each user must determine relative responses for the individual instrument. 

Generation of test atmospheres of organic vapours by the syringe injection technique Generation of test atmospheres of organic vapours by the permeation tube method On-site validation of sampling methods... 

MDHS 3 Generation of test atmospheres of organic vapours by the syringe injection technique... 

Alloys containing more than 40% rhodium, while very difficult to fabricate, are almost immune from attack by aqua regia. The Pt— lORh alloy is particularly resistant to attack by free wet chlorine such as that produced by the combustion of halogenated organic vapours. 

In sliding electrical contact applications, palladium plating has been criticised on the basis of a tendency due to its catalytic activity to cause polymerisation of organic vapours from adjacent equipment with the formation of insulating films on the surface. This effect is important in certain circumstances, but is not serious in many practical applications... 

In the previous discussion it has been assumed that the vapour is a pure material, such as steam or organic vapour. If it contains a proportion of non-condensable gas and is cooled below its dew point, a layer of condensate is formed on the surface with a mixture of non-condensable gas and vapour above it. The heat flow from the vapour to the surface then takes place in two ways. Firstly, sensible heat is passed to the surface because of the temperature difference. Secondly, since the concentration of vapour in the main stream is greater than that in the gas film at the condensate surface, vapour molecules diffuse to the surface and condense there, giving up their latent heat. The actual rate of condensation is then determined by the combination of these two effects, and its calculation requires a knowledge of mass transfer by diffusion, as discussed in Chapter 10. 

This technique bus been applied by Rhodes and Younger(107) to obtain the values of h0 for condensation of a number of organic vapours, by Pratt(92) to obtain the inside coefficient for coiled tubes, and by Coulson and Mehta(i08) to obtain the coefficient for... 

Rhodes, F.H. and Younger, K.R. Ind. Eng. Chem. 27 (1935) 957. Rate of heal transfer between condensing organic vapours and a inetal tube. 

An organic vapour is being condensed at 350 K on the outside of a bundle of pipes through which water flows at 0.6 m/s, its inlet temperature being 290 K. The outer and inner diameters of die pipes are 19 min and 15 mm respectively, but a layer of scale 0.25 mm thick and thermal conductivity 2.0 W/in K has formed on die inside of the pipes. 

Avoid the release of organic vapours or gases at any stage in the lifecycle. 

This type of catalyst is not limited to nickel other examples are Raney-cobalt, Raney-copper and Raney-ruthenium. When dry, these catalysts are pyrophoric upon contact with air. Usually they are stored under water, which enables their use without risk. The pyrophoric character is due to the fact that the metal is highly dispersed, so in contact with oxygen fast oxidation takes place. Moreover, the metal contains hydrogen atoms and this adds to the pyrophoric nature. Besides the combustion of the metal also ignition of organic vapours present in the atmosphere can occur. Before start of the reaction it is a standard procedure to replace the water by organic solvents but care should be taken to exclude oxygen. Often alcohol is used. The water is decanted and the wet catalyst is washed repeatedly with alcohol. After several washes with absolute alcohol the last traces of water are removed. 

This stirrer is not dependable for stirring operations lasting several hours the rubber tubing may stick to the shaft and may also be attacked by the organic vapours causing it to swell and allow the escape of vapours. 

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