272 J. L. Smith — Determination of the Alkalies in Silicates. 



ate of lime in three or four portions, and mix intimately after 

 each addition ; empty the contents of the mortar completely 

 upon a piece of glazed paper, that ought always to be under 

 the mortar, and introduce into the crucible. The crucible is 

 now tapped gently upon the table and the contents settled 



The crucible is then clasped by a metallic clamp in an inclin- 

 ed position, or it is placed in the upper part of the support re- 

 ferred to in the latter part of this article, leaving outside about 

 three-fourths of an inch or one inch. By means Of a snuill 

 Bunsen burner the heat is brought to bear just above the tci; 

 of the mixture and gradually carried toward the lower part. 

 until the sal-ammoniac is completely decomposed, which tak^ - 

 about five minutes ; heat is then appilied in the manner sii-:l: 

 ed, either with the blast, or with the burner referi-ed to, ac- 

 hy its own draught, and the whole kept up to bright red h 

 for from 40 to 60 minutes. It is well to avoid toointen- 

 heat. 



The crucible is now allowed to cool, when the contents wu 

 be found to be more or less agglomerated in the form of a seim- 

 fused mass. A glass rod or blunt steel point will most com- 

 monly detach the mass, which is then dropped into a platinum 

 or porcelain capsule of about 150 centimeters capacity and ^^ 

 or 80 centimeters, and distilled water added. After some time 

 the mass will slack and crumble in the manner of hme; still 

 better, this may be hastened by bringing the contents of the cap- 

 sule to the boiling point, either over a lamp or water-bath ; at 

 the same time, water is put into the crucible to slack out any 

 small particles that may adhere to it, and subsequently tiii.^ 

 is added to that in the capsule, washing off the cover of the cru- 

 cible also. 



After the mass is completely slacked, the analysis may M 

 proceeded with ; as a general thing, I prefer to allow the diges- 

 tion to continue six or eight hours, though this is not necessarv. 



If the contents of the crucible are not easily detached, «w 

 not use very much force as the crucible may be injured by i ■ 

 but fill the 'crucible to about two-thirds its capacity with water 

 bring it almost to the boiling point, and lay it in ^^^ capj^^i 

 with the upper portion resting on the edge, the lime ^ih siaj 

 in the crucible, and then may be washed thoroughly into 

 dish ; also, as before, the cover is to be washed off. ^^ 



We have now by this treatment with water, the excess < 

 lime slacked into a hydrate, and some of the lime comDiiK 

 with the silica and other ingredients of the silicate in an imp 

 pable form. In solution, there is an excess of chlonde ore. 

 cium formed in the operation, and all the alkalies ongina - 

 contained in the mineral, as chlorides. All that now remai ^ 



