138 Messrs. Wanklyn and Cooper on the 



pendicularly on the first plane of the prism, the angle i being 

 then evidently zero. 



Of course the angle of the prism can also be determined 

 with this instrument ; and it is not necessary to alter any thing 

 in its arrangement or to move the prism. We have only to 

 clamp the telescope in a position of about 90° to the collimator, 

 and then to observe the reflected image alternately on both 

 faces of the prism. 



In order to be able to use the instrument for other pur- 

 poses, both telescope and collimator can be shifted parallel to 

 their axes and be fixed by the screws 0'. If the instru- 

 ment is to be used as a spectroscope, one may put conveniently 

 before the objectives of telescope and collimator prisms with 

 direct vision. 



XXIII. The Moist- Combustion Process: some Reactions of Al- 

 kaline Permanganate of Potash. By J. Alfred Wanklyn 

 and W. J. Cooper*. 



ij^OLLOWINGr up our investigations (the results of which 

 -B- were communicated in the June Number of this Journal, 

 and in the Chemical Section of the British Association at the 

 Dublin Meeting last year), we have now to announce that we 

 have overcome one of the difficulties which stood in the way 

 of giving to our process absolute generality of application to 

 all organic substances. 



It will be remembered that, starting with the organic sub- 

 stance in aqueous solution, we showed that permanganate of 

 potash and excess of alkali burnt down the organic substance 

 to the state of carbonates, oxalates, and water ; and we pro- 

 posed to render the solution acid, and so, as was well known, 

 would burn down the oxalates to carbonates. At the Dublin 

 Meeting we announced that although this answers very well 

 in many cases, yet in certain classes of cases acetates ap- 

 peared among the products of oxidation; and when once pro- 

 duced, acetates resisted further oxidation. 



We have now managed to oxidize the acetates, by the 

 simple process of using considerable excess of permanganate 

 and raising the temperature some 60 or 80 degrees above the 

 boiling-point of water. Under these conditions acetate of pot- 

 ash yields carbonate of potash, and apparently no oxalate what- 

 ever. 



There is a difficulty, however, attendant on the use of these 



* Communicated by the Authors. 



