46o Notices respecihig Neiv Books. 



cf about 60\ and at the base in about 120°; and the 

 latter at the summit in 30", and ai the base in 130°. When 

 the supeialjundani acid has been saturated so as to produce 

 tartrat cf potash, the primitive form is ahopether diflerent ; 

 it is a rectangular tetrahedral prism, of 'a hich the height 

 being one, the sides of the terminal faces will be to each 

 other as four to five ; most commonly the summit is dihe- 

 dral, from the replacement of one of the solid angles of 

 the primitive crvstni by a plane (?'. e. dihedral in conse- 

 quence of one of the solid angles beinsr replaced or rather 

 superseded bv a plane), which makes the terminal face an 

 angle of 16-2'' 3S': frequently the triangular faces of the 

 pyramid become very narrow trapezoicUl faces, by the 

 increase of two opposite planes : and this is one of the 

 more usual varieties of tbifi salt. 36 parts of supertartrat of 

 potash require 15 7 pans of subcarbonat of potash for their 

 satiira^tion, instead of 12 j)arts as directed by the College." 



The soda tartarizala of the College, or more properly 

 tartras sodce ct polas\cp, is vagutlv described by Dr. 

 Powell as its crystals being prisms of eiuht or ten unequal 

 sides; but its "primitive crystal is a right rhombic prism 

 of 80^ and 100", the edges of the prism are difierentiv. re- 

 placed so as to render it sometimes hexahedral, or octohe- 

 dral, but more frequently decahedral or dudecahedral." 

 "The primitive crystal of sulphat of soda appears to be a 

 right rhombic prism of about 72° and 103". It is fre-- 

 quently dijlicult to distine;uish the planes of the prism, on 

 account of their being deeply channt'.ed. The terminal 

 faces of these crvslals are often replaced by a dihedral sum- 

 mit with triangular faces, ocrruing on the edges of i 72°; 

 and this variety has probably given rise to the opinion, that 

 the primitive form of this salt is a cuneiform octohcdron : 

 but as the planes of the summit make with the edges of 

 72° an angle of about 137^, they meet each other at 86°, 

 whereas in the supposed crystal it would be 108\ The 

 pyramid also frequently becomes hcxahedral,.by the occur- 

 rence of four additional faces upon the edges of the ter- 

 minal faces, with which they form an angle of about 1 23°." 



There are many more iinportanl facts and observations 

 in this volume, but the above are sufficient to convince our 

 readers that it 's very well worthy their perusal. With the 

 exception of two or three inaccurate expressions, and a few 

 manipulations in which dispatch has superseded oeconomy, 

 it evinces such talents, chemical knowledge, and great ac- 

 curacy, as would do honour to any chemical philosopher. 



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