ALKALIMETRY.

appendix.]

301

apparatus is then placed on one scale of a balance, together with the other little tubecontaining the pyrosulite, and exactly weighed.

“The cork of A is then somewhat raised to allow the little tube with the manganeseto fall into the flask. The evolution of carbonic acid commences immediately, andcontinues until all the manganese is decomposed. When the operation begins*to geton more slowly, the flask, A, is placed in boiling water, and allowed to remain thereuntil no more bubbles appear. The little wax-stopper is then removed* from a, theflask, A, taken out of the hot water, and suction applied to d, until the sucked airtastes no longer of carbonic acid. The apparatus, after having been allowed to cool,is wiped dry, and replaced in the original scale, where the little tube with the pyro-lusite still remains; weights are then substituted for the loss of carbonic acid. Thenumber of centigrammes required, divided by three, directly indicates the per-centageamount of peroxide of manganese ( vide Section 32). The centigrammes substitutedfor the loss of carbonic acid are then removed from the balance, and the little tubewith the pyrosulite is thrown into A. (The little wax-stopper must of course pre-viously be replaced on a). If no fresh evolution of carbonic acid takes place, themanganese examined consists of pure pyrosulite, and the experiment is at an end. Butshould a fresh evolution of carbonic acid take place, the operation must be furtherconducted, and brought to a close, exactly as just stated ( vide supra). The apparatusis then replaced on the balance, with an additional weight of three grammes on thesame scale. If this is sufficient to restore a perfect equilibrium, no loss of acid hastaken place; the manganese, indeed, contains other matters in admixture, but onlysuch as do not consume any acid. But if the scale with the apparatus sinks, this is acertain sign that a portion of the acid has beeil lost by combining with the oxides whichthe manganese under examination contains. The number of centigrammes requiredto restore the perfect equilibrium of the balance, multiplied by 0-6114, immediately,indicates how much anhydrous sulphuric acid has been wasted in the decomposition of100 parts of the manganese under examination. The same number, multiplied by0-333, indicates the amount of acid wasted in every 100 parts of sulphuric acid em-ployed for the decomposition of the manganese in question. The same number, multi-plied by 0-5552, indicate how much anhydrous hydrochloric acid would be wasted inthe decomposition of 100 parts of the manganese. The same number, multiplied by0-333, indicates also how much acid would be wasted in every 100 parts of hydrochloricacid employed for the decomposition of the manganese.

“ These figures result from the following equations :—

“I. 275 (eq. of carbonic acid) : 501 (eq. of sulphuric acid) =the carbonic acid ob-tained minus (in proportion to the sulphuric acid used) : x.

£=this carbonic acid X tj-OI, i. e. X 1-822.

Thus, the number obtained for x indicates the amount of sulphuric acid correspondingto the amount of carbonic acid obtained minus.

“ II. 2-98 of manganese: 100=® of equation I.: x.x=x of I. X e. X 0-33557.

“ The x of the first equation tells us how much sulphuric acid has been wasted withoutcontributing to the decomposition of 2-98 grammes of the manganese; the x of thesecond equation tells us the same for 100 parts of manganese.

“ If, therefore, the amount of carbonic acid obtained minus be directly multiplied bythe product of the quotients of I. and II.,

1-822 and 0-33557,

i. e. with 0-61141 (the number given above), the amount of anhydrous sulphuric acidwasted in the decomposition of every 100 parts of manganese will immediately befound.

“ III. 5-47 (the amount of sulphuric acid used) :

100=the x of I.: x.a;=thex of I. X -MMS, i. e. X 0-18282.

“ Of 5-47 of sulphuric acid, the x of I. has been wasted, 100 corresponds to the xof III.

“ The x of III. is, therefore, found directly by multiplying the amount of carbonicacid obtained minus with the product of the quotients, 1-822 and 0-18282, i. e.=0-33301.

“The figures for hydrochloric acid are found in the same manner (4-967 of hydro-chloric acid must be taken instead of 5-47 of the sulphuric acid)."f

* “ This must of necessity be done while the flask is still standing in the hot water, or else the sul-phuric acid will recede upon the apparatus being removed from the hot water.”

t New Methods of Alkalimetry , and of determining the Commercial Value of Acids and Manganese.By Drs. C. It. Fresenius and H Will. Edited by J. Lloyd Bullock: pp. 123-128.