Hourly weight

Starting Compounds, Experiments, ments, Hours Weight, Surface, Gas Pressure,... 

By using the most stable polychelate—the one synthesized using ferric chloride and a milling time of 96 hours—weight loss was only about 30% even at 990° C. The residue obtained showed some interesting properties, such as electrical conductivity and chemical resistance. 

Estimated from a space velocity range of 0.5-3.0. Space velocity here is defined as (weight of oil feed per hour)/(weight of catalyst in reactor), since catalyst volume is not fixed in the fluid bed mode of operation. 

The reduction time for 1 g. of oxide (contained in a boat) is 1-2 hours. Weight control is necessary, since prolonged heating at high temperatures produces some further reduction to NbO. 

Cumulative time in mill (hours) %Weight loss/hour... 

Relative volatihty of plasticizers can be determined by this method. Plasticizers are placed in a circulating air oven on a rotating table. The oven is set to either 105 or 155°C and the samples are cooled and weighed after 2,4, and 24 hours. Weight loss is calculated and reported in percent of plasticizer loss between time intervals, as a loss relative to rmit area of ejqtosed surface, or as an average volatility rate (amount lost per surface area and time). Results depend on control of temperatore and air flow. It is crrstomary to compare different plasticizers in the same experiment to avoid interference of experimental conditions. 

Weight loss % hours Weight loss Z hours... 

Time-weighted exposure. This is the time-weighted average concentration for a normal 8-hour workday or 40-hour workweek to... 

Benzene. Pure benzene (free in particular from toluene) must be used, otherwise the freezing-point is too low, and crystallisation may not occur with ice-water cooling alone. On the other hand, this benzene should not be specially dried immediately before use, as it then becomes slightly hygroscopic and does not give a steady freezing-point until it has been exposed to the air for 2-3 hours. Many compounds (particularly the carboxylic acids) associate in benzene, and molecular weights determined in this solvent should therefore be otherwise confirmed. 

Aluminium oxide. The commercial material, activated alumina, is made from aluminium hydroxide it will absorb 15-20 per cent, of its weight of water, can be re-activated by heating at 175° for about seven hours, and does not appreciably deteriorate with repeated use. Its main application is as a drying agent for desiccators. 

Freshly distilled ethyl formate must be used. Commercial ethyl formate may be purified as follows. Allow the ethyl formate to stand for 1 hour with 16 per cent, of its weight of anhydrous potassium carbonate with occasional shaking. Decant the ester into a dry flask containing a little fresh anhydrous potassium carbonate and allow to stand for a further hour. Filter into a di flask and distil through an efficient fractionating column, and collect the fraction, b.p. 53-54° protect the receiver from atmospheric moisture. 

Place a mixture of 0-5 g. of finely powdered thiourea, 0-5 g. of the alkyl halide and 5 ml. of alcohol in a test-tube or small flask equipped with a reflux condenser. Reflux the mixture for a j)eriod depending upon the nature of the halide primary alkyl bromides and iodides, 10-20 minutes (according to the molecular weight) secondary alkyl bromides or iodides, 2-3 hours alkyl chlorides, 3-5 hours polymethy lene dibromides or di-iodides, 20-50 minutes. Then add 0 5 g. of picric acid, boil until a clear solution is obtained, and cool. If no precipitate is obtained, add a few drops of water. RecrystaUise the resulting S-alkyl-iso-thiuronium picrate from alcohol. 

Into a 750 ml. round-bottomed flask furnished with a reflux condenser place a solution of 34 g. (18-5 ml.) of concentrated sulphuric acid in 100 ml, of water add 33 g. of di-n-butyl cyanamide and a few fragments of porous porcelain. Reflux gently for 6 hours. Cool the resulting homogeneous solution and pour in a cold solution of 52 g. of sodium hydroxide in 95 ml. of water down the side of the flask so that most of it settles at the bottom without mixing with the solution in the flask. Connect the flask with a condenser for downward distillation and shake it to mix the two layers the free amine separates. Heat the flask when the amine with some water distils continue the distillation until no amine separates from a test portion of the distillate. Estimate the weight of water in the distillate anp add about half this amount of potassium hydroxide in the form of sticks, so that it dissolves slowly. 

In a 2-litre round-bottomed flask, equipped with a double surface condenser, place 60 g. of triniethylene dicyanide (Section 111,114) and 900 g. of 50 per cent, sulphuric acid (by weight). Reflux the mixture for 10 hours and allow to cool. Saturate the solution with ammonium sul phate and extract wit-h four 150 ml. portions of ether dry the ethereal extracts with anhydrous sodium or magnesium sulphate. Distil off the ether on a water bath the residual glutaric acid (69 g.) crystallises on cooling and has m.p. 97-97-5°. Upon recrystalhsation from chloroform, or benzene, or benzene mixed with 10 per cent, by weight of ether, the m.p. is 97 -5-98°. 

Heat a mixture of hexamethylene dicyaiiide with 15 times its weight of 50 per cent, sulphuric acid by weight under reflux for 10 hours. The acid crystallises out on cooling. Filter oflF the suberic acid upon a sintered glass funnel, and recrystallise it from acetone m.p. 141-142°. The yield is 90 per cent, of the theoretical. 

Pimelic acid. Heat a mixture of 18 g. of pentamethylene dicyanide and 250 g. of 50 per cent, sulphuric acid by weight in a 750 ml. round-bottomed flask under reflux for 9 hours. INIost of the pimehc acid separates from the cold reaction mixture. Filter oflF the crystaUine acid upon a sintered glass funnel. Saturate the filtrate with ammonium sulphate and extract it with three 50 ml. portions of ether. Dissolve the residue on the filter (which is shghtly discoloured, but is fairly pure pimehc acid) in the combined ethereal extracts, dry with anhydrous sodium or magnesium sulphate, and remove the ether by distiUation. Recrystallise the residual sohd acid from benzene containing 5 per cent, of ether. The yield of pure pimehc acid, m.p, 105-106°, is 22 g. 

Ethyl benzoate hydrogen chloride as a catalyst). Pass dry hydrogen chloride (Section 11,48,1) into a 600 ml. round-bottomed flask containing 116 g. (145 ml.) of absolute ethyl alcohol, cooled in an ice bath, until the increase in weight is 6 g. Add 30 g. of benzoic acid and reflux the mixture for 4 hours. Isolate the pure ester, b.p. 212-214°, as described for Methyl Benzoate. The yield is 32 g. 

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