ON MINIMETRIC ANALYSIS. 189 



difference in one case is 0*0005 gramme of carbonic acid, 

 as every cub. centim. of tbe oxalic acid solution was equal to 

 O'ooi gramme of carbonic acid. This was repeated times 

 without number, and served as a basis for a new mode of 

 using the baryta- and lime-water test. To this method of 

 analysis I have given the name Minimetric. We ascertain 

 the smallest amount of air required to produce a precipitate 

 of a given density. 



The same method can be employed to determine hydro- 

 chloric acid, sulphuric and sulphurous acids, sulphuretted 

 hydrogen, &c. 



Estimation of Carbonic Acid by Minimetric Analysis. 



1st. For Definite Amounts of Carbonic Acid. — If we 

 shake a bottle containing 644 cub. centims. or 23 ounces 

 of common air, we obtain a precipitate such as that de- 

 scribed above. Now, if air containing twice as much car- 

 bonic acid were to be put into the bottle, the precipitate 

 would be twice as great, but we could not ascertain its 

 value by the eye. We cannot even make a probable ap- 

 proach to it. If, however, we used a bottle just half the 

 size of the first, the air being still twice as bad as the first 

 specimen, we should have a precipitate exactly the same, 

 because in fact the amount of carbonic acid would be exactly 

 the same. If the air were four times as bad. We should 

 then use a bottle four times smaller, and obtain a precipitate 

 also exactly the same as the first ; and so on down to the 

 smallest dimensions. I go here in the belief that, although 

 we cannot approach at all closely when endeavouring to 

 obtain the comparative value of two precipitates, ive can 

 retain in the memory with great exactness the character of 

 one precipitate of a given density. 



If, then, we wish the air of a place to be kept at any 

 one given state of purity, we should require only to have a 



