Boiling wells

A dry reflux set-up is used with a three neck flask allowing a thermometer and sep funnel to be attached to the reaction flask. The thermometer is placed well below the surface of the flask contents. If the temperature rises above 55°C ice will need to be used to cool things down a bit So the three neck flask will be sitting in an ice bath on the stir plate before we begin. If ether is used instead of THF the ether will boil well before 50°C is reached giving a better indication of how hot things are getting. 

Vaporization cavitation repre.sents about 70% of all cavitation. Sometimes it s called classic cavitation . At what temperature does water boil Well, this depends on the pressure. Water will boil if the temperature is high enough. Water will boil if the pressure is low enough. 

To avoid errors due to the presence of extraneous sulphur compounds in the cotton, the latter may be boiled for half a minute—before testing— with 10% caustic soda solution and then boiled well with water. It must, however, be borne in mind that the reaction of the sulphide dyestuffs is thus rendered less distinct. Use should not be made in this test—unless after thorough washing—of test-tubes or flasks previously used for the hydrosulphite reduction, since the latter results in the deposition on the glass of an imperceptible layer of sulphur, which may lead to evolution of hydrogen sulphide in presence of the boiling solution of the tin salt. 

Nonpurge and trap extraction, such as liquid-liquid microextraction, can be used for many volatile compounds with boiling points well below 200°C. Similarly, the purge and trap method can be used for compounds boiling well over 200°C, especially when the purging chamber is heated. 

Mercury is a liquid at room temperature, so the melting point must be below 298 K (25°C). Mercury boils well above room temperature, so the boiling point must be well above 298 K. These facts fit the calculation. 

Write the question in your journal. Then begin to wait. Sooner or later an idea, an image, or words will form in your mind. (Hint The more relaxed you are about the arrival of this response, the sooner and more easily it will come. You know the expression A watched pot never boils Well, an eagerly awaited soul answer may not boil either. Wait patiently—and not too avidly—for your soul to come to you. 

Because the temperature at atmospheric pressure cannot exceed 100°C, there is little risk of baking peroxide-containing residues to their decomposition point. For solvents boiling well below 100 C the thermal efficiency of direct steam injection is at least as good as for other methods of evaporation. 

Weld weld [alter, of obs. E well to weld, fr. ME wellen to boil, well, weld] (1599) v. A metallic bond between hke or unlike metals. 

Table 11.1 lists the boiling points of some common amines. Methylamine and eth-ylamine are gases, but primary amines with three or more carbons are liquids. Primary amines boil well above alkanes with comparable molecular weights, but below comparable alcohols, as shown in Table 11.2. Intermolecular N—H- -N hydrogen bonds are important and raise the boiling points of primary and secondary amines but are not as strong as the O—H- -O bonds of alcohols (see Sec. 7.4). The reason for this is that nitrogen is not as electronegative as oxygen (see Table 1.4).

Remember the saying a watched pot never boils Well, this is why without the lid on, the heat just escapes rather than staying to raise the water s temperature. This is also why steam can scald a person. All that heat that had to be absorbed to produce the steam is still present in the steam in the form of kinetic energy. If that steam touches your skin, all that extra energy is transferred back to your skin as heat. 

Compilation of azeotropic data as well as other physical properties including melting and boiling points. 

Liquid ammonia. This can be prepared by compressing ammonia gas. It has a boiling point of 240 K and is an excellent solvent for many inorganic and organic substances as well as for the alkali metals. Liquid ammonia is slightly ionised. ... 

The most important source of helium is the natural gas from certain petroleum wells in the United States and Canada. This gas may contain as much as 8 % of helium. Because helium has a lower boiling point Table 12.1) than any other gas, it is readily obtained by cooling natural gas to a temperature at which all the other gases are liquid (77 K) almost pure helium can then be pumped off. The yearly production in this way may be many millions of m of gas. but something like 10 m per year is still wasted. 

Chapter 6). We note, however, that there is not a smooth increase in the magnitude of these properties as the atomic number increases the metals seem to divide into two sets, Sc-Mn and Mn-Zn with peaks at Ti-V and Co-Ni. and this is well illustrated by a graph of boiling point against atomic number (Figure 13.1). 

Place 0 5 ml. of acetone, 20 ml. of 10% aqueous potassium iodide solution and 8 ml. of 10% aqueous sodium hydroxide solution in a 50 ml. conical flask, and then add 20 ml. of a freshly prepared molar solution of sodium hypochlorite. Well mix the contents of the flask, when the yellow iodoform will begin to separate almost immediately allow the mixture to stand at room temperature for 10 minutes, and then filter at the pump, wash with cold w ater, and drain thoroughly. Yield of Crude material, 1 4 g. Recrystallise the crude iodoform from methylated spirit. For this purpose, place the crude material in a 50 ml. round-bottomed flask fitted with a reflux water-condenser, add a small quantity of methylated spirit, and heat to boiling on a water-bath then add more methylated spirit cautiously down the condenser until all the iodoform has dissolved. Filter the hot solution through a fluted filter-paper directly into a small beaker or conical flask, and then cool in ice-water. The iodoform rapidly crystallises. Filter at the pump, drain thoroughly and dry. 

Assemble the apparatus shown in Fig. 6o. A is a 500 ml. bolt-head flask connected by a knee-tube B to a water-condenser C, to the lower end of which is fitted the adaptor D. In view of the low boiling-point of the ethyl bromide, it is essential that the various portions of the apparatus are connected together by well-bored, tightly fitting corks. (For this reason, the apparatus shown in Fig. 23(0), p. 45, is preferable.)... 

Add 20 ml. of a mixture of equal volumes of acetic anhydride and glacial acetic acid to 10 ml. (10 3 g.) of aniline contained in a 150 ml. conical flask. Fit a reflux water-condenser to the flask, and boil the mixture gently for 10 minutes. Then pour the hot liquid into 200 ml. of cold water, stirring the latter well... 

When the ij hours boiling is complete, preheat a Buchner funnel and flask by pouring some boiling water through the funnel with the filter-paper already in position, and then quickly filter the boiling solution. Transfer the filtrate to a beaker to cool, and then wash the insoluble residue of diphenylurea on the filter twice with hot water, and drain thoroughly. Cool the filtrate in ice-water the monophenylurea separates as colourless needles. Filter at the pump and drain well. Recrystallise the crude product from boiling water, as in the previous preparation. Yield of monophenylurea, 2 5-3 g. m.p. 147°. 

Hydrolysis to p-Nitroaniline. For this purpose use 70 sulphuric acid, the usual reagent employed for the hydrolysis of anilides (p. 108). Add 5 g. of the recrystallised />-nitro-acetanilide to 30 ml. of 70%sulphuric acid, and boil the mixture gently under a reflux water-condenser for 20 minutes. Then pour the clear hot solution into about 150 ml. of cold water, and finally add an excess of sodium hydroxide solution until precipitation of the yellow p-nitroaniline is complete. Coo the mixture in ice-water if necessary, and then filter at the pump, wash well... 

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