114 W. Gibbs—Analytical Notices. 
2. On the estimation of magnesium as pyro-phosphate. 
All works on quantitative analysis recommend the precipita- 
tion of magnesium in the form of ammonia-magnesic phosphate, 
from cold solutions, by disodic phosphate. I find it more con- 
venient, if not more accurate, to employ microcosmic salt as a 
precipitant, and to precipitate from concentrated and boiling 
solutions. After cooling ammonia is to be added, and the pro- 
cess then continued in the usual manner. The following analy- 
ses were made under my direction by Mr. C. E. Munroe to test _ 
the method. In the tirst series pure magnesic sulphate was 
precipitated at a boiling heat and in concentrated solutions by 
microcosmic salt, no ammopic chloride being present. 
1. 0°6430 gr. gave 0°2914 gr. Mg, P, 0, = 9°85. 
2. 1°1523 gr. “ 0°5210 gr. = ot et * 
3. 0°7064 gr. “ 0°3181 gr. i a. 8°78, 
4, 08081 gr. “ 0°3666 gr. 35 == 9°80. 
The formula S0,Mg+70H, requires 9°76% The mean of 
the four analyses is 0-04% too high. In a second series the 
same process was employed, but ammonic chloride was add 
to the magnesic solution before precipitation. In this manner: 
5. 0°5448 gr. gave 0°2461 gr. Mg, P,0, = 9°76. 
6. 0°6684 or. “ 03026 gr  “ = 9°78. 
7. 0°7610 gr. “ 0°3442 gr. $ == 9°78. 
8. 0°6408 gr. “ 0°2906 gr. " => 9°78; 
The mean of the four analyses gives 9°78%, or 0°02% too high. 
Two-analyses were then made by precipitating the boiling 
solution of disodic phosphate after adding ammonic chloride. 
In this manner: 
9. 0°5407 gr. gave 0:2536 gr. Mg,P,0, = 10°13%. 
10. 0°8305 gr. “ 0°3881 gr. * = 10°10%. 
This method must therefore be wholly rejected, the mean 
error being +0°35%. . 
The same process was then repeated, only the precipitated 
ammonia-magnesic phosphate at first obtained, after addition of 
ammonia water and perfect subsidence, was redissolved 1 
dilute chlorhydric anid, and again precipitated by ammonia 
n this manner: 
11. 0°5916 gr. gave 02686 gr. Mg, P,0, = 9°79%. 
12. O-7371 gr. “ 03340gr.  ‘ = 9°79%. 
e error is here only +0°03%, but the method is longer 12 
its application and less convenient than that given above with 
microcosmic salt. This last may, I find, be used with equal 
advantage in precipitating manganese from hot solutions. ‘The 
precipitate is crystalline, and the process is more convenient 
