161 
Tur Destruction oF PLATINUM CRUCIBLES THROUGH THE 
IqenitTIon oF Macanestum AMMONIUM PHOSPHATE. 
By Rosert HE. Lyons. 
Platinum is not oxidized in the air at any temperature, nor attacked 
by any single acid, yet there are many substances that attack and combine 
with it at comparatively low temperatures. 
It sometimes happens that a platinum crucible is cracked or is fused 
through during the burning of the filter paper containing magnesium am- 
monium phosphate, or during the final ignition required to convert mag- 
nesium ammonium phosphate into magnesium pyrophosphate. This has 
again and again been a source of annoyance and expense to the phosphate 
analyst. The break down of the crucible is not due to invisible mechanical 
defects in the crucible, nor to the quality of the platinum or platinum al- 
loy used in its construction. The cause of these occasional accidents is to 
be found in the reduction of the phosphate through incorrect procedure in 
burning or igniting the paper in connection with the precipitate, or, indi- 
rectly and less frequently, by failure to observe the well-established condi- 
tions for properly precipitating and washing magnesium ammonium phos- 
phate. 
The direction for the treatment of the magnesium ammonium phos- 
phate residue given in the texts and handbooks, at the disposal of the 
writer, is by no means sufficient to enable the inexperienced operator to 
safely use a platinum vessel in this operation. The notes on the use and 
eare of platinum ware, published by Baker & Co., Heraeus and other 
platinum smiths, do not suggest the possibility of a mishap from the igni- 
tion of magnesium ammonium phosphate in a platinum crucible. The notes 
furnished by the Baker Co. have long contained the statement: “Organic 
matter containing phosphorous should not be ignited in platinum dishes, 
as it affects the platinum seriously.” This ‘serious affect’ is the same as 
that noticed occasionally in connection with the ignition of magnesium 
ammonium phosphate in platinum crucibles, and is caused by the combina- 
tion of reduced phosphorous with the platinum, forming platinum phosphide. 
