STATE. CEOLOEISI, 115 
driven off and the residue filtered off. The sulphuric acid is precipitated 
by means of barium chloride as given in the fusion method. 
' Volumetric Methods —In addition to the method of determining the 
sulphur as barium sulphate, we have several methods of determining 
the sulphur from sulphides volumetrically. The best known of these 
methods employs a standard iodine solution using starch as an indicator. 
It is extremely useful in the examination of blast furnace slags and is © 
very rapid. (See N. W..Lord, “Notes on Metallurgical Analysis,” p. 102.) 
THE EXAMINATION OF NATURAL CEMENTS. 
The analytical methods employed in the analysis of natural cements 
are practically the same as those used in analyzing limestones with the ex- 
ception that fusion must be resorted to in order to bring about complete 
solution of the sample. 
Weigh out one gram of the finely ground sample and mix intimately 
on glazed paper with 3 grams of sodium carbonate. ‘Transfer to a plati- 
num crucible and raise slowly to a red heat over a Bunsen flame and 
after ten minutes, heat over the blast lamp for five minutes. Place crucible 
in casserole containing about 150 cc. of water, boil till mass has softened 
and has left the crucible, replenishing the water evaporated. Add hydro- 
chloric acid till distinctly acid, keeping casserole covered with watch glass. 
Now add a few drops of nitric acid to solution and evaporate to dryness. 
The residue is heated at about 110° C. in a tile lined oven for one hour. 
After cooling, add 10 cc. of hydrochloric acid, let stand for a few minutes 
and dilute with boiling water. Filter and transfer filtrate back into casse- 
role, evaporate to dryness as before and heat at 110° C-. till all hydrochloric 
acid has been expelled. ‘Take up again with tocc. hydrochloric acid, dilute 
with boiling water and filter through the filter used in the first separation 
of silica, thus adding any silica not separated in the first evaporation. 
In rapid technical work only one evaporation is made, but this never 
removes all of the silica present. 
Now bring the filtrate to boiling and add ammonia to slight 
excess; boil for a few minutes and filter, washing several times 
with hot water. Remove funnel from above the filtrate and wash the 
precipitate of aluminum and ferric hydroxide into a clean beaker with 
hot water. Follow this by washing the filter with hot water containing 
20 per cent. hydrochloric acid, allowing solution to run into the second 
beaker. Heat filtrate and precipitate in the fresh beaker till all of the iron 
and alumina is dissolved. Dilute, make slightly ammoniacal to repre- 
cipitate the iron and alumina, boil for a minute and allow to settle. Decant 
clear liquid through the filter used before, taking care to wash it first 
with water containing a little ammonia. 
The filter should be a 11 cm. ashless filter. Wash twice by decanta- 
tion in this manner, using boiling hot water. If the precipitate is very 
