3870 = L. F. Wood—Arsenie as Pyroarseniate of Magnesia. 
Il. Filtrate = 146 c.c. Washwater = = 50 «e 
Wt. of Mg, As,0O, 
4637 grams, 
vee Peat a ass rs nl 0076.58 
Wt. As, 0, calculated = 03008 « 
IL. Filtrate = 106 - C. Washwater — oe = 58 C.C. 
Wt. of Mg, As,O 4576 
“« MgNH , AsO, -LAq. n.0 tage 
Wt. As,O, calculated = 0°2992 
In the following analysis the solution was allowed to stand 
four days after the addition of the alcoholic-magnesia solution 
and the alcohol. The result indicates the precipitation of 
magnesic hydrate or carbonate | 
ay. Weight of 85°42 O, = 0°4962 
“ MgNH,AsO,+Aq = 00083 
Wt. As,O, calculated = 0°3212 
In order to avoid this error in the following analyses, the 
first precipitate after filtration was-dissolved in chlorhy ricacid, 
and reprecipitat ed with an excess of ammonia water; and a 
quantity of alcohol equal to half the bulk of the liquid was 
added. The results were the same, whether this pee 
was filtered immediately or after the lapse of 24 hou Prob- 
ably, if a second precipitation is employed, the apyare = might 
be added penecaeely during the first precipitation instead of 
waiting 24 hou 
Results obtained by two precipitations. : 
V. 1st filtrate = 109 c.c. 2d filtrate = 68 ¢.c. . 
ash water = 45 c.c. 
Wt. cof, .Mg,As,0, = 0°4630 
MgNH, ‘AsO,-FAq = 0? hci 
Wt. As,O, calculated =0° - 02992 
VI. 1st filtrate — 125 c.c. 2d filtrate — 64 ¢.¢. 
Wash water = 
c.c. 
Wt. of Mg, As,O — 0°4596 
“ MgNH, AsO, +Aq = 0° o124 
Wt. As,O, calculated = 0° - 02999 
VII. ist filtrate — 165 c.e. 2d filtrate = 
Wash water = 45 ac. 
Wt. of Mg, As,O, = 04615 
“ MgNH,AsO,+Aq = 00099 
Wt. of AsO, calculated = 0-2999 
