78 



parts, the remaining 60 divisions should bo filled up with water, and the whole being 

 well stirred, 100 parts of the acid liquor will now contain as much real acid ag was 

 eontainod before in the 50 parts. 



35. The acid may now be labelled simply, ' Test or Normal Sulphuric Acid' Each 

 one hundred alkalimetrical divisions, or 1,000 water-grains' measure of it, contain one 

 equivalent, or 40 grains of real sulphuric acid; and, consequently, each 100 alkali- 

 metrical divisions of it will neutralise one equivalent, or 31 grains <of soda, 47 of pot- 

 ash, 17 of ammonia, 28 of lime, and so forth, with respect to any other base. 



36. The stock of test or normal sulphuric acid should, as usual, be kept in well- 

 stoppered bottles, in order to prevent concentration by evaporation. By keeping in 

 tho flask containing it a glass bead, exactly adjusted to the specific gravity of 1-032, 

 the operator may always ascertain, at a glance, whether the acid requires readjusting. 



37. With a Schuster's alkalimeter, it is convenient to prepare the test acid of such 

 a strength that, according as it has been adjusted for potash or for soda, 10 grains of 

 it will exactly saturate one grain of one or the other of these bases in a pure state. 

 It in considered that the alkalimoter may be charged with a known weight of any 

 of the other sulphuric test acids of a known strength. Suppose, for example, that tho 

 test sulphuric acid taken have a specific gravity of 1-032, we know, as we have just 

 shown, that 1*032 grains weight of that acid contains exactly one equivalent of pure 

 sulphuric acid =40, and is capable, therefore, of neutralising one equivalent of any 

 base ; and, consequently, by taking a certain weight of this acid before beginning 

 the assay, and weighing what is left of it after the assay, it is very easy to calculate, 

 from the quantity of acid consumed in the experiment, what quantity of base has been 

 neutralised. Thus a loss of 21-96, 60'70, 33-29 grains' weight of this test acid 

 represents one grain of potash, of ammonia, of soda respectively, and BO on with the 

 other bases. 



38. The operator being thus provided with an appropriate test acid, we shall now 

 describe how he should proceed with each of them in making an alkalimetrical assay 

 with potash. 



In order to obtain a reliable result, a fair average sample must be operated upon. 

 To secure this the sample should be taken from various parts of the mass and at once 

 put in a wide-mouth bottle, and well corked up until wanted ; when the assay has to 

 be made, the contents of the bottle must be reduced to powder, so as to obtain a fair 

 mixture of the whole ; of this weigh out 1,000 grains exactly or less, if that quantity 

 cannot be spared and dissolve them in a porcelain capsule, in about 8 fluid 

 ounces of distilled hot water, or in that proportion ; and if there be left anything like 

 an insoluble residue, filter, in order to separate it, and wash it on the filter with small 

 quantities of distilled water, and pour the whole solution, with the washings and 

 rinsings, into a measure divided into 10,000 water-grains' measure. If the water used 

 for washing the insoluble residue on the filter has increased the bulk of the solution 

 beyond 10,000 water-grains' measure, it must be reduced by evaporation to that 

 quantity ; if, on the contrary, the solution poured in the measure stands below the 

 mark 10,000 water-grains' measure, then as much water must be 

 31 added thereto as will bring tho whole mass exactly to that 



point. In order to do this correctly, the cylindrical measure 

 should stand well on a table, and the under or lower 

 line formed by the liquid, as it reaches the scratch 32 



10,000, is taken as the true level. 



39. This being done, 1,000 grains' measure of the 

 filtrate, that is to say, one-tenth part of the whole 

 solution, is transferred to a glass beaker, in which 

 the saturation or neutralisation is to be effected, 

 which is best done by means of a pipette capable 

 of containing exactly that quantity when filled up to 

 the scratch, a. In order to fill such a pipette it is 

 sufficient to dip it into the alkaline solution and to 

 euck up the liquor a little above the scratch, a; 

 the upper orifice should then be stopped with tho 

 first finger, and by momentarily lifting it up, the 

 liquor is allowed slowly to fall from the pipette 

 back again into the 10,000 grains' measure until its 

 level reaches exactly the scratch, a. The last drop II 



which remains hanging from the point of the pipette 

 may be readily detached by touching the sides of the glass measure with it. The 1,000 

 grains being thus rigorously measured in tho pipette should then be transferred to tho 

 glass beaker, in which tho neutralisation is to take place, by removing the finger 

 altogether, blowing into it to detach the last drop, and rinsing it with a little water. 



