Text-book of medical and pharmaceutical chemistry . ample, suppose gm. of alcoholbe taken, and we find ofair after making the necessary cor-rections. Now, o. I gm. of hydro-gen measures 1116 at 0° 760 mm. pressure. We nowcompare these volumes and wehave ^ = 23, or the hydrogen occupies 23 times the volume ofan equal weight of alcohol , one meter of hydrogen understandard condition weighs ,acrith. One of hydro-gen then weighs .0000896 gm. ; of hydrogen will gm. By dividing theweight of the alcohol taken, , by the weight
Text-book of medical and pharmaceutical chemistry . ample, suppose gm. of alcoholbe taken, and we find ofair after making the necessary cor-rections. Now, o. I gm. of hydro-gen measures 1116 at 0° 760 mm. pressure. We nowcompare these volumes and wehave ^ = 23, or the hydrogen occupies 23 times the volume ofan equal weight of alcohol , one meter of hydrogen understandard condition weighs ,acrith. One of hydro-gen then weighs .0000896 gm. ; of hydrogen will gm. By dividing theweight of the alcohol taken, , by the weight of ofhydrogen, we obtain 23 as thedensity of the alcohol vapor. As the density of the alcohol vapor is thus seen to be 23,cular weight must be 46. We may determine the molecular weight of substances thatwill not wholly volatilize without decomposing, by the methodof Raoult. This method consists in determining the amountof lowering of the freezing point of a solvent, due to thesubstance dissolved in it. The lowering of the freezing point. Victor Meyers Apparatus. its mole- 300 MEDICAL CHEMISTRY. is proportional to the quantity of the solid in this law is not perfectly uniform for inorganic substances,it is uniformly so with organic substances, with very few excep-tions. Let I gram of a compound be dissolved in loo grams ofa liquid with which it forms no chemical union. Let themolecular weight of this compound be represented by M. Ifwe now cause the solution to freeze, we shall observe that itfreezes at a lower temperature than the solvent. This depressionof the freezing point we will represent by D. If we multiplythis depression by M, the molecular weight of the compound,we shall have the depression for M grams of the substance, /. e.,the molecular weight expressed in grams. Let this be repre-sented by T. Then we shall have D X M ~- T. Raoult foundthat the value of T is very nearly constant for the samesolvent. Tlie value of T for water is 19, for aceti
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