450 Mr. Griffin on the Constitution of 



Observations on the Table of Carbonate of Soda. 



The strongest solution of carbonate of soda prepared at 

 62° F. has the sp. gr. of 1*166, and a chemical strength of 

 185°. Its formula is nearly NaO, C0 2 + 33H 2 0. A solution 

 of sp. gr. 1*16657 deposited crystals while weighing at 62° F. 

 The solution of sp. gr. 1*166, if cooled a little below 62° F., 

 also deposits crystals. The exact point of saturation is diffi- 

 cult to hit. I made many trials with perfectly pure materials, 

 and always weighed a quantity that filled a bottle of the 

 capacity of 3000 grs. of water. I believe that the sp. gr. 1*166 

 is very near the truth. It differs considerably however from 

 the usual quotations. Dr. Thomson states the specific gra- 

 vity of a saturated solution at 58^° F. to be 1*07516. This 

 is no doubt a misprint for 1*17516. Dr. Henry quotes the 

 specific gravity at the temperature of the atmosphere to be 

 1*26. This also seems to be a misprint for 1*16. 



The greatest amount of condensation occurs in the solution 

 of sp. gr. 1*166, coincident with the greatest chemical strength 

 and greatest density, as is the case with solutions of all the 

 fixed alkalies described in this memoir. 



The measure of the test atom of anhydrous carbonate of 

 soda is 38*66 septems, or a little above that of anhydrous 

 sulphuric acid. The measure diminishes rapidly as the salt 

 combines with water, and in a solution of 1° the atomic volume 

 is reduced to —70*38 septems, showing a difference of 109 

 septems. The condensation produced by the combination of 

 carbonate of soda with water exceeds that produced by the 

 hydration of sulphuric acid. Thus, 1 test atom of each sub- 

 stance, combined with different proportions of water, effects 

 the following condensations, expressed in septems :— 



The fraction which + 1 indicates the mean specific gravity 

 of 100° of carbonate of soda is (1*4659^-25*866 = ) -056673. 



Thgre is a particular hydrate of carbonate of soda, the che- 

 mical degree of which is about 90, where the condensation is 

 equal to the volume of the test atom of the anhydrous salt. 

 If a solution be made at this stage of dilution, of course the 

 substance will dissolve without altering the bulk of the water. 



