14 



Prof. T. S. Humpidge. 



rected by this important generalisation. In all fnture determinations 

 of the atomic weight of an element, the position which the element 

 should occupy in the periodic arrangement mnst receive due import- 

 ance, and had I fully recognised this two years ago, I should perhaps 

 have stated my conclusions and criticisms less positively than I did. 



Appendix A. 



On the Composition of the Double Carbonate of Glucinum and 



Ammonium. 



An analysis of this important compound has been published by 

 Debray,* but the formula he obtained being somewhat complex, I 

 have prepared and analysed the pure substance. A strong solution of 

 ammonium carbonate was digested with moist glucinum carbonate at 

 a gentle heat until saturated. The clear solution was then heated 

 until it became cloudy, and any excess of ammonium carbonate decom- 

 posed, then again filtered and mixed with its own bulk of strong 

 alcohol. The crystals, which only separated slowly and adhered 

 firmly to the walls of the containing vessel, were drained, washed 

 with alcohol, and dried between filter-paper. 



The analyses of two separate specimens gave the following 

 results : — 





I. 



II. 



Mean. 



Calculated. 



BeO 



18-77 



19-22 



19-00 



18-40 



COo 



4213 



43-16 



42-65 



43-00 



(NH 4 ) 2 0.... 



26-39 



26-25 



26-31 



25-41 



H (diff.) . . 



1271 



11-37 



12-04 



13-19 





100-00 



100-00 



100-00 



100-00 



which correspond to the formula 2(GlC0 3 ,Am 2 C0 3 ),Gl(OH) 2 + 2H 2 0. 

 This resembles the formula obtained by Debray, viz., 



3(GlC0 3 ,Am 2 C0 3 ),Gl(OH) 2 , 



but contains more water. Both of my specimens were dry crystalline 

 powders, without a trace of adhering alcohol, and with a faint odour 

 of ammonia. Specimen II had been kept for several weeks in a 

 stoppered bottle. 



* " Ann. d. Cliim." [3], xliv, 5. 



