302 Mr. Griffin on the Constitution of 



specific gravity, its atomic weight, the volume of its anhy- 

 drous atom, are all matters of indifference. The sole regu- 

 lating particular is the extent of condensation per decigallon 

 expressed in septems. Every septem of condensation per deci- 

 gallon, effected in any solution, increases the specific gravity 

 by -001 (water being = 1*000). 



It is easy to test the accuracy of this principle by facts. 

 If we divide the differences given in Table III, by '001, we 

 find the number of septems that correspond to the condensa- 

 tion per decigallon in each solution. And if the condensation 

 per decigallon is divided by the number of test atoms known 

 to be present in a decigallon of each solution, the product 

 shows the amount of condensation effected by each test atom, 

 and that product corresponds with the number given in co- 

 lumn 6 of Table II. 



The following calculation, relating to acid of 10 atoms or 

 1000° of strength, also substantiates this principle. 



To .... . "035252 = fraction indicating the mean specific 



gravity of 100° of acid, 

 Add .... '01 2698 = condensation per atom in solutions of 

 1000° of acid: see Table III. 



•047950 

 Multiply by 10 = number of test atoms of acid per 



decigallon. 



Gives . . . -479500 



Add .... 1 '000000 = specific gravity of water. 



Result . . . 1*479500= real specific gravity of acid of 1000°. 



I hold these results to prove that anhydrous sulphuric acid 

 has no fixed atomic volume in solution. There is, neverthe- 

 less, a means of indicating the volume of an atom of anhy- 

 drous acid in solution, which is free from fallacy, and well- 

 adapted to practical purposes, — I allude to that exhibited in 

 column 7 of Table II. The numbers in this column are all 

 chemically equivalent, and show how many measures of any 

 strong acid must be taken to produce, by dilution with water, 

 the atomic measure of another weaker acid. Thus, 47'437 

 septems, the atomic measure of SO 3 , H 2 0, diluted with water 

 to the bulk of 58*276 septems, produces the hydrate SO 3 , 

 ?H ci O ; or diluted to the bulk of 73*403 septems, it produces 

 che hydrate S0 3 + 3H 2 ; or diluted to the bulk of 1000 sep- 

 tems, it produces acid of 100°. The condensation that occurs 

 in these dilutions has been estimated and thrown out, so that 

 we deal only with the practical results. The atomic measure 

 of a solution is therefore a definable manageable quantity. 



