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     [H] 
 
     Organic Compounds - Osmolality vs Volume.  S.H. Shakman  
Relative observed maximum osmolality (OS) for a majority of organic
compounds listed by CRC* may be approximated (within 10%) as
relative theoretical increase in solute volume (DV) attributable to
full hydration of assumed component ions, calculated in accord with
Flint's description, volumetric definition and equation
DV=(gpl/k)((Vhz/2Vaz)-1)**, when gpl=grams-per-liter anhydrous
solute, k=520, and Vhz & Vaz = sums of hydrated and anhydrous ionic
volumes (Vh,Va).
 MAXIMUM OSMOLALITY vs VOLUMETRIC INCREASE,ORGANIC COMPOUNDS
  
  Compound    Assumed Ions       gpl*  OS*    DV   OS/DV 

   ACETIC ACID CH3-,CO++,OH-     375.6  7.20   6.85 1.05 

   ACETONE     CO++,2CH3-         98.5  1.767  1.80  .98 

   ETHANOL     CH3-,CH2++,H+,O-- 593.2 26.62  24.97 1.07 

   FORMIC ACID CO++,H-,OH-       733.2 23.13  22.46 1.03 

   GLUCOSE    3CHOH++,3CHOH--    337.4  2.577  2.28 1.13 

   GLYCEROL   2CH2++,CHOH--,2OH- 439.4  8.33   9.10  .92 

   LACTOSE     C6H10O5,6CHOH++--  83.5   .266   .26 1.02 

   METHANOL    C+4,3H-,OH-       595.9 51.8   52.50  .98 

   OXALIC ACID CO++,CO--;OH-,OH+  40.7   .587   .64  .92 

   2-PROPANOL 2CH3,H+,COH-3      231.1  5.87   6.40  .92 

   CCL3COOH    C+4,OH+,CO--,3Cl- 172.9  2.051  1.95 1.05 

   UREA        CO++,2NH2-        494.5  9.47   9.06 1.05 

 

*CRC HANDBOOK,1985-6,D221-D269.  **FLINT,L.H., Behavior Pat- terns
of Hydration(1964): Wa[anhydrous weight]=2(Z[atomic #]
+C[valence]); Wh[hydrated weight]=Wa+18H; H[hydration #]=23n -(Z+C)
[H=23 to 0, n=1 to 4]; Vh=Wh/(1+(Wa/Wh)); Va=Wa/2.

 
Supercedes 1987 AAAS Pac.Div.Abstract,"Max.Osmolality...". 
Proposed for 1988 AAAS Meeting, AAAS # 0925.15; withdrawn 25 Sept.
1987.

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