﻿478 Scientific Intelligence. 



rotation of water in the free and in the combined form suggested 

 the possibility of determining by means of the magnetic rotation 

 whether the water in hydrated compounds existed as such or 

 whether it was present in actual combination. If the former, the 

 numbers obtained should represent the value for the compound 

 plus that of the water ; if the latter, lower values would be 

 obtained. Thus if a molecule of formic acid were mixed with a 

 molecule of water we might have either HCOOH + H 2 0, or 

 HC(HO) s ; the molecular rotation being in the first case 2 -6 71 

 and in the second not over 2*340. Experiment gave 2*666. 

 The molecular rotation of acetic acid, under the same conditions, 

 was 3*554, of propionic acid 4*512, and of ethyl alcohol, 3*787; 

 the calculated values on the supposition that the water exists as 

 such in them, being 3*525, 4*462 and 3*780 respectively. "The 

 foregoing results," the author says, " are further evidence of the 

 fact that although thermal changes and alterations of density 

 result from chemical action, yet that they themselves are not 

 evidence of chemical action." With sulphuric acid, whose 

 molecular rotation was 2*315, it was found that the addition of 

 one molecule of water brought this value to 3*188, two molecules 

 to 4*113, and three to 5*064 ; the calculated values of course 

 being 3*315, 4*315 and 5*315. There is hence an increase of 

 rotation in the first case of 0*873, in the second of 0*925 and in 

 the third of 0*951. These numbers indicate that the largest 

 amount of combination takes place when the first molecule is 

 added and therefore it seems probable that only one chemical 

 compound results from the action of water on sulphuric acid, 

 namely, (HO) 4 SO. With regard to water of crystallization, the 

 author calls attention to the want of consistency as to the pres- 

 ence or absence of such water in the simple salts of metals 

 belonging to the same class; such for example as the salts of 

 silver, potassium and sodium. These inconsistencies are so great 

 that it is impossible in his opinion to believe that water of 

 crystallization has any relationship to chemical combination. It 

 appears to him that the relationship is a purely physical one, its 

 presence with the compound being necessary for the building up 

 of the crystalline form which can most readily be produced. 

 "If a salt by itself," he says, "can produce the most easily 

 formed crystalline structure, it will naturally do so and be anhy- 

 drous ; but if on the other hand it cannot do so, it will associate 

 itself with that number of molecules of water with which it can 

 most readily produce the crystalline form." — J. Ghem. Soc, xlix, 

 777-790, October, 1886. G. e. b. 



4. On the Behavior of Alkali-earths and their Hydrates to 

 dry Carbon dioxide. — Scheibler has undertaken a series of ex- 

 periments in order to ascertain the action which dry carbon 

 dioxide exerts upon the alkali-earths and their hydrates. The 

 following are his conclusions : 1st. Perfectly dry carbon dioxide 

 does not combine either with the caustic anhydrous oxides of the 

 earth-metals or with their mono-hydrates ; or with hydrated ba- 



