ALKALIMETRY.

123

aqueous solution of carbonate of soda should exactly saturate the contents ofan alkalimeter, divided into 100 parts, filled with 1000 water-grains’ weight of asolution of 1 part of concentrated sulphuric acid in 10 parts, by measure orvolume, of water, so that the litmus solution becomes coloured very slightlyred. But should only go volumes of the acid be required to saturate the sodasolution, it is evident that to render the acid solution of the required strength,there must be added to every go volumes of it 10 volumes of water.

The acid solution adjusted for the assay of soda should be of such astrength that 100 divisions of an alkalimeter capable of containing 1000 grs.of water will exactly neutralise 170-98 (in practice 171) grs. of pure anhydrouscarbonate of soda, or 100 grs. of pure soda.

The alkalimeter described by Faraday is suited to the estimation of potashor soda, or of either or both of their carbonates. He says, “ Let the tuberepresented in the margin, Fig. 14, have 100 grs. of water weighed into it;then let the space it occupies be graduated into 100 equal parts, and everyten divisions numbered from above downwards. At 22'1 parts, or p77-99 parts from the bottom, make an extra line a little on oneside, or even on the opposite side of the graduation, and writeat it with a scratching diamond soda; lower down, at 48-62parts, make another line, and write potash; still lower, at54-43 parts, a third line carb. soda; and at 65 parts a fourth,marked carb. potash. It will be observed that portions aremeasured off beneath these marks in the inverse order of theequivalent number of these substances, and consequentlydirectly proportionate to the quantities of any particular acidwhich will neutralise equal weights of the alkalies and theircarbonates. As these points are of great importance, it will beproper to verify them by weighing into the tubes first 350, then5 I 3 ' 8 , and lastly 779-9 grs. of water, which will correspond wr«w-with the marks if they are correct, or the graduation may be cARasoo*-laid down from the surface of the four portions of fluid whenweighed in, without reference to where they fall upon the general eorAsirscale. The tube is now completed, except that it should beobserved whether the aperture can be perfectly and securelycovered by the thumb of the left hand, and if not, or if therebe reason to think it not ultimately secure, then it should beheated and contracted until sufficiently small.” The acid foruse with this alkalimeter should have a sp. gr. of 1-1268; it mayhe prepared by mixing 1 part by weight of sulphuric acid of 1-82 sp. gr. with4 parts of water. This acid having been poured into the alkalimeter tothe point marked carbonate of soda should neutralise exactly 100 grs. ofPure anhydrous carbonate of soda dissolved in water.

The most perfect method, however, results from the preparation of a normalucid, so adjusted that 100 alkalimetrical divisions will exactly neutralise1 equivalent of every base. This acid should have a sp. gr. of 1-032, and mayhe prepared in the manner described by Dr. Ure as follows:—

“ Take 53 grs. (1 equivalent) of pure anhydrous neutral carbonate of soda,und dissolve them in about 1 fluid ounce of water. Prepare, in the meantime,the test sulphuric acid by mixing 1 part by measure of concentrated

14.

r-

=-is

=-25=—30=- 35

I - *

=-45

=—50

I- 55

E—60£-65=—70|-75£-80I- 85=—90

95