CANE SUGAR. 



185 



The average deviation from these mean ratios is 0.15 per cent, while 

 the largest single deviation — that of the 0.6 normal solution at 25° — is 

 0.3 per cent. It is obvious from the relations pointed out above, that 

 between 0° and 25° the osmotic pressure of cane-sugar solutions — rang- 

 ing in concentration from 0.1 to 1.0 weight-normal — obeys the law of 

 Gay-Lussac for gases. In other words, within the limits designated, 

 the temperature coefficients of gas and osmotic pressures are identical. 

 So much must be conceded on the basis of the experimentally demon- 

 strated facts — whatever may hereafter be found to be true of solutions of 

 cane sugar which are more or less concentrated, or of other substances. 



Table 61. — Cane sugar. Calculated gas pressures of solute between 0° and 80°. 



Cone. 



0.1 

 0.2 

 0.3 

 0.4 

 0.5 

 0.6 

 0.7 

 0.8 

 0.9 

 1.0 



if 



2.227 2. 



4.453 4 



6.680 6 



8.906 9 



11.13311 



13.35913 



15.585J15. 



17.81218. 



20 . 038 20 . 



22 . 265J22 . 



267 

 535 

 802 

 069 

 337 

 604 

 871 

 139 

 406 

 674 



10°. 15°. 20 



2 



4 



6 



9 



11 



13 



16 



18 



20 



23 



.308 

 .616 

 .925 

 .233 

 .541 

 .849 



2 

 4 

 7, 

 9 



11 



14. 



349 

 698 

 047 

 396 

 745 

 094 



2. 



4. 



7. 



9. 

 11. 

 14. 



390 

 780 

 170 

 560 

 950 



25°. 30°. 40°. 50°. 60°. 70°. 80° 



2 

 4 

 7 

 9 

 12 



431 

 862 

 292 

 723 



15716. 

 466:18. 



774 

 082 



21 

 23 



443116 

 792,19 

 14121 

 49023 



33914 

 72917 

 11919 

 509 21 

 89924 



15412 

 58514 

 01517 

 44619 



877122 

 30824 



472 2, 



943 5. 



415 7. 



88610. 



35812 



83015 



30117. 



773 20 



24422. 



71625 



553 

 107 

 660 



21310 

 76713 

 320,15 

 87318 

 426121 

 980|23 

 533126 



635 

 270 

 905 

 540 



2. 



5 



8. 



10 



717 

 433 

 150 



17513 

 81016 

 44519 

 080i21 

 71524 

 35027.167,27 



86711 

 58413 

 30016 

 01719 

 73422 

 45025 



798 

 597 

 395 

 194 



" 



2.880 

 5.760 

 8.640 

 11.520 

 .99214.401 

 .79017.281 

 .58920.161 

 .38723.041 

 .18625.921 

 .984 28.801 



Table 63. 



The 0.1 normal solution at 0° appears to present an exception to the 

 rule that the ratio of osmotic to gas pressure for that concentration is 

 about 1.083 at temperatures under 25°. The pressure found was 2.462, 

 which gives a ratio to calculated gas pressure of 1.106; 

 whereas, in order to conform to the rule which holds 

 for the 0.1 normal solution at 5°, 10°, 15°, 20°, and 

 25°, the pressure should be about 2.227x1.083 equals 

 2.413. The difference, 2.462 minus 2.413 equals 0.049 

 atmosphere, is probably too large to be accounted for 

 as due to experimental error — especially in a solution 

 so dilute that unavoidable errors of meniscus and 

 capillary depression are of little moment. More- 

 over, thermometer effects which are a source of 

 sensible error at other temperatures are insignificant 

 in a properly constructed bath at 0°. It is to be remembered in this 

 connection, as possibly explaining the apparent anomaly, that at 0° the 

 0. 1 normal solution is within less than 0.2° of its freezing temp erature. It 

 is desirable to investigate more concentrated solutions at temperatures 

 equally near their freezing-points, but such investigations will obviously 

 be attended by great, if not insurmountable, experimental difficulties. 

 The problem of maintaining constant temperatures below 0° is in itself 

 a difficult one. Moreover, at temperatures below the freezing-point of 

 the solvent, the osmotic pressures of solutions can be measured only 

 by differential methods; that is, the cells must be surrounded by solu- 



