|
UüC 60 1.63 : 543.24
IS0
I NT ERN AT I ON A L O RG A N IZATl O N FO R STAN DA RD IZATl O N
IS0 RECOMMENDATION
R 848
PHOSPHORIC ACID FOR INDUSTRIAL USE
DETERMINATION OF CALCIUM CONTENT
VOLUMETRIC METHOD
1st EDITION
October 1968
COPYRIGHT RESERVED
The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
---------------------- Page: 1 ----------------------
BRIEF HlSTORY
The IS0 Recommendation R 848, Phosphoric acid for industrial use - Determination of calcium content
Volumetric method, was drawn up by Technical Committee ISO/TC 47, Chemistry, the Secretariat of which is
held by the Ente Nazionale ltaliano di Unificazione (UNI).
Work on this question by the Technical Committee began in 1960 and led, in 1966, to the adoption of
a Draft IS0 Recommendation.
-
In December 1966, this Draft IS0 Recommendation (No. 1109) was circulated to all the IS0 Member Bodies
for enquiry. It was approved, subject to a few modifications of an editorial nature, by the foilowing Member Bodies :
Austria Israel Spain
Belgium Italy Switzerland
Brazil
Japan Thailand
Bulgaria Korea, Dem. P. U. of Turkey
Chile Korea. Rep. of U.A.U.
Czechoslovakia Netherlands United Kingdom
France New Zealand U.S.S.R.
Germany
Poland Yugoslavia
Hungary
Romania
India South Africa, Rep. of
No Member Body opposed the approval of the Draft
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 Council, which decided,
in October 1968, to accept it as an IS0 RECOMMENDATION.
-2-
---------------------- Page: 2 ----------------------
ISO/R 848-1%8(E)
IS0 Recommendation R a48 October 1968
PHOSPHORIC ACID FOR INDUSTRIAL ,USE
DETERMINATION OF CALCIUM CONTENT
VOLUM ETR IC METHOD
1. SCOPE
This IS0 Recommendation describes a volumetric method for the determination of the calcium content in
phosphoric acid for industrial use.
2. FIELD OF APPLICATION
The general method is applicable to the determination of the calcium content in phosphoric acid for industrial
use.
2.1 Special case
Phosphoric acid for industrial use containing polyphosphoric acids (see section 8).
NOTE. - In case there is no certainty of absence of polyphosphoric acids, carry out the determination according to
the procedure of the special case directly.
3. PRINCIPLE
Precipitation of calcium as calcium oxalate at pH 4 ?: 0.3.
Filtration of the precipitate and purification by dissolving in hydrochloric acid and re-precipitation under the
same operating conditions.
Oxidimetric titration in sulphuric acid solution by means of potassium permanganate.
4. REAGENTS
Distilled water or water of equivalent purity should be used in the test.
4.1 Sulphuric acid, approximately d = 1.84, 96 (m/m) or 36 N solution.
4.2 Hydrochloric acid, approximately d = 1.19, 37 (m/m) or 12 N solution.
4.3 Ammonium hydroxide, approximately d = 0.91, 25 (m/m) or 15 N solution.
Ammonium chloride, saturated solution at room temperature (approximately 300 g/l).
4.4
4.5 Ammonium oxalate, 40 g/l solution.
Dissolve 4 g of ammonium oxalate monohydrate in water and dilute to 100 ml.
4.6
Potassium permanganate, 0.1 N standard volumetric solution (see Note, section 7).
-3-
---------------------- Page: 3 ----------------------
ISO/R 848-1%8(E)
5. APPARATUS
Ordinary laboratory apparatus and
5.1 pH-meter, fitted with a giass electrode.
5.2 Witt’s apparatus, with a 250 ml beaker (see Figure opposite).
Funnel, approximately 60 mm in diameter, with sintered glass disk of porosity grade between
5.3
5 and 15 pm.
6. PROCEDURE
6.1 Test portion
Weigh by difference, to the nearest 0.01 g, approximately 50 g of the test sample.
6.2 Determination
6.2.1 Preparation of sample solution. Place the test portion (6.1) in a beaker of suitable capacity
(250 ml, for example), add 50 ml of water and 20 ml of the hydrochloric acid solution (4.2);
bring to the boil, cool and transfer quantitatively to a 500 ml one-mark volumetric flask. Dilute
to the mark, mix thoroughly and filter, if necessary, on a dry filter collecting the filtrate into a
dry container.
6.2.2 Firstprecipitation of calcium oxalate. Transfer 100.0 ml of the filtrate (6.2.1) to a beaker of
suitable capacity (250 ml, for example).
Add 10 ml of the ammonium chloride solution (4.4) and 50 ml of the ammonium oxalate solution
(4.5). Adjust the pH to 4 f 0.3 by addition, drop by drop, of the ammonium hydroxide solution
(4.3), stirring during the operation and checking the pH by means of the pH-meter (5.1 ).
Bring to the boil and continue boiling for 10 minutes, then let the precipitate settle for about
20 minutes.
Decant the supernatant liquid onto the funnel (5.3) using the Witt’s apparatus (5.2), leaving most
of the pre
...