462 Mr. Griffin on the Constitution of 



Observations on the Table of Sal-Ammoniac. 



I have adopted for the weight of the test atom of sal-am- 

 moniac Berzelius's number for muriatic acid, added to Thom- 

 son's number for ammonia; my object being to afford a 

 means of comparing solutions of sal-ammoniac at given 

 strengths with those of muriatic acid and ammonia at the 

 same strengths, quoted in other sections of this memoir. 



The strongest solution of sal-ammoniac at 62° F. has the 

 specific gravity of 1*077333 and the chemical strength of 

 306°. Its formula is probably H 2 C1 2 , N 2 H 6 + 16H 2 0. This 

 solution gives a considerable deposit of crystals when cooled 

 to 59° F. The measure of the test atom of the anhydrous 

 salt is 6223 septems. When existing in the solution of 306° 

 its measure is increased to 70* 10 septems. When in a solu- 

 tion of 1° its measure is diminished to about 50 septems. At 

 an intermediate point, somewhere about 12°, the measure of 

 the atom in solution is the same as that of the anhydrous 

 atom. Hence sal-ammoniac has no fixed volume in solution, 

 but possesses the property of causing expansion in strong so- 

 lutions and condensation in weak solutions. 



The atomic measure of sal-ammoniac is never the same as 

 the joint measure of muriatic acid and ammonia. The differ- 

 ences at different stages of dilution are as follow : — 



Messrs. Playfair and Joule seem to be of opinion that when 

 we know the atomic measure of a compound, A B, and that 

 of one of its components, A, then, by taking the difference, 

 we can find the true measure of the other component, B. It 

 is clear, however, that this is not the case with sal-ammoniac ; 

 for this salt, when at its state of greatest expansion, has a 

 smaller atomic measure than ammonia plus muriatic acid when 

 the latter is at its point of greatest condensation. Hence any 

 attempt to determine the atomic measure of ammonia from a 

 knowledge of the atomic measures of muriatic acid and of 

 sal-ammoniac must lead only to bewilderment. 



