Practical methods for determining molecular weightsChemical Publishing Company, 1899 - 235 pages |
Common terms and phrases
amount of substance asbestos atoms Auwers Beckmann benzene Benzoic acid Biltz boiling-jacket boiling-point method boiling-vessel bulb burner calculated capillary Chem chemical chloride complex molecules concentration condenser convenient cork covolume curve cylinder device diameter dilute solutions dissociation dissolved substance double molecules drop Dumas Dumas method easily employed ether ethyl alcohol experiment filled flame flask formic acid formula freezing Freezing-point lowering freezing-point method freezing-vessel gas-displacement method gauze glass tube grams heat of vaporization heating-box hydroxyl group Ibid introduced investigated J. H. van't Hoff layer mercury Meyer molecular depression molecular volume molecular weight molecular weight determinations molecules naphthalene Nernst Nitrobenzene obtained p-cresol phenols phys pipette placed platinum pressure pycnometer Raoult reservoir ring rise in boiling-point side tube soluble solvent stearic acid stirrer sufficient tablet thermometer thermostat tion Traube undercooling values vapor-density determinations vapor-jacket vaporizing vessel Ztschr
Popular passages
Page 164 - M is a jacket of asbestos, 12 cm. high and 1 ^ cm. thick, over the top of which the rate of boiling can be observed very satisfactorily. It is constructed by bending a thin board of asbestos tightly around the tube (A), and fixing it in place by means of copper wire. Thick asbestos paper is then wound around this, until the desired thickness is reached. The apparatus is supported on a small iron tripod (S), 8 cm. in diameter, on which rests an asbestos ring (R), about 9 cm. in external diameter....
Page 165 - ... is much greater than in the case of a solution. This is strictly analogous to what is observed with the freezingpoint method. Here, the time necessary to establish the temperature of the equilibrium between the solid and liquid phases of the pure solvent, is always much greater than for a solution. Before taking a reading on the Beckmann thermometer, it is always necessary to give it a few sharp taps with a lead pencil, and indeed this should be done occasionally while the mercury is rising,...
Page 167 - ... prevents the condensed solvent from coming in contact with the thermometer until it has been re-heated.
Page 163 - A,, which is 2 or 2-^ cm. in diameter, by means of a cork. When it is desired to protect the solvent from the moisture in the air, the top of the condenser tube should be provided with a tube containing calcium chloride or phosphorus pentoxide. During an experiment, the vessel A is closed above by a cork, through which the Beckmann boiling-point thermometer T passes. M is a jacket of asbestos, 12 cm. high and i£ cm. thick, over the top of which the rate of boiling can be observed satisfactorily....
Page 164 - B, surrounded by an ordinary metallic cone, /, to protect the small flame from the effect of air currents. The glass vessel, A, is shoved down until it comes in contact with the wire gauze. Under these conditions a very small flame suffices when low-boiling solvents are employed, and not a large flame is required when a solvent like aniline is used. Carrying Out a Determination.
Page 164 - ... cm. The platinum plates are then introduced into the platinum cylinder, the end of the tube (A) closed with a cork, and the ground-glass stopper inserted in A. The apparatus is then set in a small beaker glass and weighed. The solvent is then introduced, and the whole reweighed. Great care must be taken that not enough solvent is employed to boil over from one side of the platinum cylinder to the other. In case a laboratory is not provided with a balance capable of weighing accurately 200 or...
Page 163 - These are made by cutting foil into pieces about y± cm. square, bending the corners alternately up and down, to prevent them from lying too closely upon one another, and serrating the edges with scissors, to give a greater number of points from which the boiling can take place. The bulb of the thermometer is thus entirely surrounded by metal at very nearly its own temperature, except directly above.
Page 14 - ... stopper is driven out of the tube, and the liquid is soon converted into vapour. To effect an equal distribution of heat, the water is continually moved by means of a stirrer (p, m, n). As soon as the temperature has reached the point at which the determination is to be made, the volume of the vapour, the temperature of the water, and the height of the barometer are noted, and at the same time the temperature of the air and the difference between the height of the mercury inside and outside the...