170 Mr. G. Williams on Emeralds and Beryls. [Apr. 26, 



tate, or 1*07 per cent., a quantity which might partly arise from in- 

 sufficient washing, partly from a variation from the mean weight in the 

 filter ash, and also from a trace of alumina. 



Experiment III. — 0*1603 gramme of glucina, known to contain a little 

 alumina, was dissolved in hydrochloric acid, neutralized as usual, and 

 treated with 50 cub. centims. of solution of carbonate of ammonium. The 

 residue of alumina weighed 0*0071. In two days 0-0067 gramme more 

 was obtained. On filtering 16 days afterwards only 0*0017 gramme, 

 or 1*06 per cent., was obtained. In one year after that time the solu- 

 tion was again filtered, the deposit weighed 0-0012 gramme, or 

 0*75 per cent., being only one third of the weight of the ash of one 

 filter paper. 



Experiment IV. — 0*3846 gramme of pure glucina was treated in the 

 usual manner with 80 cub. centims. of carbonate-of -ammonium solution. 

 The whole dissolved perfectly in a few minutes. The solution was kept 

 for three weeks and then filtered. The precipitate weighed 0*0003 gramme, 

 or 0*08 per cent., after deducting the filter ash. If it were necessary 

 these examples could be multiplied ; but they seem amply sufficient to 

 enable an answer to be given to the question at the head of this section. 

 "We may therefore affirm unhesitatingly that one decigramme of pure 

 glucina is permanently soluble in 25 cub. centims. of a saturated solution of 

 carbonate of ammonium. 



It was necessary, in order to make these experiments complete, to 

 ascertain whether great variations in temperature influenced the solubility 

 of glucina in solution of carbonate of ammonium. That glucina was 

 permanently soluble at about 15° C. there remained no doubt ; but there 

 might still be a tendency in glucina to assume an insoluble form at higher 

 temperatures. To determine this question it was essential to use a tem- 

 perature many degrees higher than that ever reached by the atmosphere. 

 Eor this purpose 4 decigrammes of pure glucina were dissolved in the 

 usual way in 100 cub. centims. of solution of carbonate of ammonium. 

 15 cub. centims. of this solution were transferred to a glass tube, which 

 was then sealed and heated to 100° for two days. Hie solution remained 

 perfectly clear. 



2. Does Glucina confer its solubility on Alumina ? or does Alumina 

 confer its insolubility on Glucina ? 



It is very easy to come to an erroneous conclusion on this point, 

 because if a mixture of the two earths in solution of carbonate of am- 

 monium be filtered at once a certain amount of alumina will, in that case, 

 pass through the filter ; but it settles out in a short time, and, if glucina 

 be present, it will be accompanied by some of that earth. 



The following experiment was made to affix a quantitative value to 

 the amount of alumina soluble in carbonate of ammonium when no 

 glucina was present to influence its solubility. 



