1834.] 



Assay of Saltpetre. 



190 



V\\.— Assay of Saltpetre according to the principle established 

 by M. M. Bottc et Riffault in France. 



This process consists in using a dissoluent of salts of earthy bases 

 and of muriate of Soda which at the same time will not act upon 

 the nitrate of potasse, and in leaving it undisturbed would shew 

 the exact quantity of pure nitre contained in any given quantity of 

 groQgh Saltpetre ; this dissoluent is water fully saturated with pure 

 nitre ; if care is taken to obtain the saturated solution at the time 

 of using it, in atully saturated state. 



The following is the method to be pursued. 



Method of prepar- ^^^^ ^"^^owi two or three pounds of pure nitre 

 ing th'- saturated pounded and sifted, and throw it by degrees into 

 aoiuti m. ^ copper vessel tinned inside about 12 inches 



deep, and 5 inches diameter pouring in at the same time, good 

 water heated to 126 degrees of Fahrenhiet, to be well stirred, and 

 left for three or four hours or during the night, there ought always 

 to be a portion of pure nitre not dissolved at the bottom, and the 

 solution ought never to he used without stirring it well up from the 

 bottom, and allowing it only one minute to settle, each time of 

 using it.* 



The Saltpetre received is to be collected in a heap, and well 

 mixed, and a quantity taken from different parts of the mass, from 

 which a sample; or any number of samples of 100 drams avoirdu- 

 pois each is to be taken, the saltpetre taken for assay must be well 

 bruised in a mortar. 



One of these samples of 100 drams is to be placed in a glass 

 vessel (a common finger glass or cooler is well adapted for this 

 operation) and half a pint of the saturated solution poured upon 

 it, and constantly stirred with a glass rod for 15 minutes, then 

 allow it to settle for an instant, and pour off the surface water into 

 a paper filter placed in a funnel over any vessel, this paper filter is 

 necessary in order to retain any nitrate of potasse which may escape 

 by carelessness in pouring off the surface water. 



The Saltpetre in the glass vessel is then to be washed a second 

 time with a quarter of a pint of the saturated solution, and stirred 

 with a glass rod constantly for 15 minutes, allowed to settle and 



* In France where tMs mode of assay is pursued, an instrument called an 

 Ar^ometre, with a thermometer are used to ascertain, that the solution is 

 fully saturated up to the temperature of the place before using it, but the 

 assay may be conducted with great accuracy withosjt these instruments it 

 the rules here laid dowm are strictly observedo 



