168 Messrs. Calvert and Johnson on the Chemical Changes which 
evaporated to dryness, and heated at 200° C. to render the 
silica insoluble. The whole was then treated with water slightly 
acidulated with acetic acid, and on the silica being separated 
by filtration, the amount of sulphate, and consequently of 
sulphur, was determined from the weight of sulphate of baryta 
obtained. 
Phosphorus.—We also attached great importance to the exact 
valuation of this body, because, like sulphur, its presence even 
in small quantities is most injurious; the more so, as such 
minute quantities as a few thousandths, more or less, will com- 
pletely alter the value of iron for many uses. To determine 
phosphorus, the process which we followed was similar to that 
employed for the sulphur ; with this difference, that we added 
some muriatic acid, and to the liquid from which we had sepa- 
rated the silica, ammonia in excess instead of acetic acid, as we 
had done in the analysis of sulphur. The liquid was allowed to 
stand, to see if any alumina separated; and if not, we added 
hydrochloric acid in excess, then pure chloride of calcium, and 
then ammonia again, when phosphate of lithe having the following 
formula, PO® 3CaO, was precipitated, from which the quantity of 
phosphorus was calculated. We always took care to operate on 
such a bulk of fluid as to prevent the precipitation of any sulphate 
of lime, and we also washed rapidly to prevent any carbonate of 
lime being formed. We verified this method several times during 
our analysis, by determining the amount of lime in our precipi- 
tates, and the amount of phosphoric acid, by M. Reynoso’s 
process. 
Aluminium.—If there was any aluminium, it was separated 
during the last process and its amount determined. We also 
made several fusions of iron dissolved in aqua regia and evapo- 
rated with a mixture of alkaline carbonates to which we had 
added a little caustic alkali, and we found no aluminium, or only 
mere traces in the iron analysed by us. 
Manganese.—5 grammes of iron were dissolved in aqua regia, 
and the whole evaporated to dryness and calcined with alkaline 
carbonates. The fused mass was treated with boiling water, and 
to the solution were added small pieces of Swedish paper to 
reduce the manganate. The iron and manganese were then col- 
lected on a filter, well washed, and then dissolved in hydrochloric 
acid. This solution was again evaporated, and heated so as to 
render the silicic acid insoluble. The residue was then treated 
with some weak hydrochloric acid, and the solution filtered to 
separate the silica. Carbonate of baryta recently prepared was 
then added to precipitate the oxide of iron; this was separated 
by filtration, and to the liquid, sulphate of soda and a little hy- 
drochloric acid were added to separate the baryta in solution ; 
