OF ARTS AND SCIENCES. 39 



0-5479 gr. gave 0098<l gr. SO^Co = 17-H7r/ cobalt. 

 0-8183 gr. gave 0-1-459 gr. SO^Co = 17-83% cobalt. 

 0-4040 gr. gave 0-2170 gr. water = 5-19<y{, hydrogen. 

 l-00(iO gr. gave 0-4005 gr. water =^ 5-09''^; bydrogeii. 

 0.4091 gr. gave 118-5 c.c. nitrogen = 2^-97% nitrog(Ui. 

 0-3035 gr. gave 109-4 c.c. nitrogen = 29-93<y^ nitrogen. 



These analyses correspond tolerably well with the emi)irical for- 

 mula, — 



Co(NIl3)A(NO,),+OII„ 

 which requires, — 



Calculated. INIean. Found. Freiiiy's formula. 



Cobalt, 2 18-55 17-S5 17-83 17-87 19-54 



Hydrogen, 34 5-34 5-14 5-19 5-09 5-03 



Nitrogen, 14 30-85 29-45 28-97 29-93 32-45 



Oxygen, 18 45-28 47-51 43-38 



In judging the analyses it must be remembered that the salt cannot be 

 recrystallized, as it is instantly decomposed by water. By standing 

 for a long time over sulphuric acid, the salt loses water and some am- 

 monia. In a salt so dried, — 



0-5088 gr. gave 0-2090 gr. SO.Co = 20-12% cobalt. 



0-3290 gr. gave 0-0859 gr. NH3 =20-11% ammonia (by boiling 



with KHO solution and titrition). 

 0-4308 gr. gave 0-1124 gr. NHg =20-09% ammonia (by boiling 



with KHO solution and titrition). 



The undecomposed anhydrous salt would contain 19-00% cobalt, and 

 would give oft' by boiling with potash 28-33% ammonia. I consider 

 the true formula of this salt * to be twice as high as that given above, 

 so that it becomes, ^ — 



Co,(NH,),,0,.(NO,),+20H,. 



Fremy found very nearly the same percentages of nitrogen and hydro- 

 gen, but a much higher percentage of cobalt, 2077%. He also found 

 that the salt is readily decomposed by water with evolution of oxyo-en. 

 In a single analysis to determine the quantity of oxygen evolved, I 

 obtained the following results: — 



* In a letter to the German Cliemical Society, I have represented tiie nitrate 

 of oxycobaltiaque as containing four atoms of ammonia to one of cobalt ; but a 

 careful revision of my analyses leads to the formula given above. Deutsche 

 Chem. Gesell. Berichte, iv. 790. 



