Mr. J. E. Reynolds on a modified Spectroscope. 129 



Sample V. — *85645 grin, gave *3353 grm. carbonic anhydride ; 

 •53245 grm. gave *1411 grm. ammonia. 



These data give the following percentage composition for the 

 five several preparations : — 



I. II. III. IV. V. 



Carbonic anhydride. 37*43 38-44 39-84 38-15 39*15 

 Ammonia . . . 28*59 . . 28*21 27*85 26-50 



The formula of the diammonic carbonate with one atom of 

 water of crystallization, 



CO 3 (NH 4 ) 2 , OH 2 , 



gives the following numbers : — 



Carbonic anhydride . . 38*60 



Ammonia 29*82 



Water 31*58 



The powder into which the diammonic carbonate passes on ex- 

 posure gave 21*66 per cent, ammonia, determined in *671 grm. 

 Theory requires for CO 3 H (NH 4 ) the number 21*52, 



XVII. On a modified Spectroscope for use in the examination of 

 Minerals. By J. Emerson Reynolds, Member of the Royal 

 College of Physicians, Edinburgh, Keeper of the Minerals and 

 Analyst to the Royal Dublin Society*. 



THE modified spectroscope presently to be described was 

 arranged some time ago by me, for the purpose of supply- 

 ing a deficiency long felt in using the ordinary form of spectrum- 

 apparatus. 



I believe all who have much employed the delicate and beau- 

 tiful mode of investigation afforded by the method of spectrum- 

 analysis, will agree with me that the ordinary single-prism 

 arrangement is by no means well suited for use in the routine 

 work of a chemical laboratory. When the eye of the operator is 

 applied to the telescope of the instrument, the slit and the flame 

 in which the test-specimen is being ignited are out of view and 

 beyond easy control. Practice will, of course, overcome much 

 of the difficulty attendant upon this circumstance; but for rapid 

 and satisfactory work it is always necessary to obtain the aid of 

 an assistant. The same objection applies with equal force to the 

 direct-vision spectroscope of M. Hofmann, excellent though this 

 instrument is in other respects. Every chemist knows how ad- 

 vantageous it is to have his apparatus entirely under his own 



* Communicated by the Author, having been read before the Royal 

 Dublin Society, December 16, 1867. 



Phil Mag. S. 4. Vol. 36. No. 241. Aug. 1868. K 



