458 Mr. Griffin on the Constitution of 



The chemical strength of the solutions that were examined 

 was determined by neutralization with pure muriatic acid, 

 the strength of which was ascertained by means of carbonate 

 of soda and nitrate of silver. The specific gravities were 

 determined by weighing the liquors in stoppered glass bottles 

 at the temperature of 62° F. I have placed side by side the 

 theoretical densities and those determined by experiment, and 

 I have added a column of differences, to show in what cases 

 and to what extent the experimental specific gravity indicated 

 a greater or lesser chemical strength than the theoretical 

 specific gravity. If in any of these solutions there had oc- 

 curred either condensation or expansion, it would be shown 

 in this column, where however are also shown all the errors 

 of experiment. These errors are very great in the experi- 

 ments on concentrated solutions, and they are unavoidable. 

 A solution of ammonia of 1000° effervesces when a warm fin- 

 ger is applied to the bottle containing it. In general the 

 specific gravity determined by experiment is too high, for 

 this reason, that when a concentrated solution is prepared 

 and adjusted to the required temperature it takes but little 

 time to transfer a graduated pipetteful of it into a stoppered 

 bottle containing water to dilute it for chemical examination ; 

 whereas, the transferring of a quantity of the undiluted so- 

 lution to a weighing bottle, the adjustment of the measure, 

 and the accurate weighing, occupy much time, occasion con- 

 siderable exposure to the air, and permit a large escape of 

 gas. Below 800° this difficulty is much less, and the differ- 

 ences are probably errors of experiment. There is however 

 one part of the Table in which the differences between the 

 computed and experimental specific gravities seem to indicate 

 the occurrence of expansion. This is between 500° and 100°, 

 and it is among solutions of this strength that Dr. Ure found 

 similar differences to exist between experimental and com- 

 puted densities ; from which differences he drew the conclu- 

 sion, that solutions of ammonia expand when they are diluted. 

 I subjoin his experiments : — 



Computed or 



mean specific 



gravity. 



•90452 



•90901) 



•91838 



•9278 



•9375 



Specific 

 gravity by 

 experiment. 



•9045 



•909 



•9177 



•9275 



•9363 



Computed or 



mean specific 



gravity. 



•94737 

 •95744 

 •9G774 

 •97826 

 •989 



Specific 

 gravity by 

 experiment. 



•9455 



9561 

 •9662 



•9768 



•9887 



•Tilloch's Philosophical Magazine, vol. lvii. 



