Aqueous Solutions of Acids and Alkalies. 



293 



Imperial Liquid Measure. Divided Decimally. 



The relation of the decigallon to the septem is the same as 

 that of the litre (kilogramme of water) to the cubic centimetre 

 (gramme of water) . 



1 litre contains 2200 septems. 



Chemical Standards. 



In speaking of chemical substances with reference to atomic 

 weights, I have used the numbers contained in the tables of 

 Berzelius, oxygen = 100. In order to be able to speak with- 

 out vagueness of certain absolute quantities of substances, I 

 use the term Test Atom to signify Berzelius's atomic weight 

 of a substance weighed in English grains. By the term De- 

 gree, I mean the hundredth part of a test atom. Thus, — 

 5*01165 grs. is 1° of SO 3 . 

 501-165 ... is 1 test atom, or 100° of SO 3 . 



In applying these measures and weights to centigrade test- 

 ing, I prepare normal test liquors of 100° of strength, in all 

 cases, by dissolving 1 test atom of the substance in so much 

 water as produces 1 decigallon of solution at 62° F. ; that is 

 to say, — 



To prepare Carbonate of Soda of 100°. — I dissolve 667*335 

 grs. of pure anhydrous carbonate of soda in distilled water, 

 dilute the solution to the bulk of about 995 septems, bring it 

 to the temperature of 62° F., and then adjust the volume to 

 exactly 1000 septems. 



To prepare Nitrate of Silver of 10°. — I dissolve 212*864 

 grs. of pure crystallized nitrate of silver in distilled water, and 

 in like manner dilute the solution at 62° F. to the bulk of 

 1000 septems. 



A centigallon of test liquor of 100° contains the tenth part 

 of a test atom of any substance. My alkalimeter, or centigrade 

 pouret, has the capacity of a centigallon, and is graduated 

 into 100 septems : hence every degree of this instrument indi- 

 cates the 1000th part of the test atom of the reagent, while, 



