Oct. 4.] THE NEW ZEALAND GAZETTE. 2919

(5) Determination of potash.

(a) Muriate of potash free from sulphates:—

A weighed portion of the sample (about 5 grams
in the case of concentrated muriate of potash or
10 grams in the case of low-grade muriate) shall
be dissolved in water, the solution shall be filtered
if necessary and made up to 500 cubic centimetres.
The potash shall be determined in 25 or 50 cubic
centimetres of the solution by the perchloric acid
method prescribed below in clause (d) of this
paragraph.

(b) Salts of potash containing sulphates:—

A weighed portion of the sample (about 5 grams
in the case of concentrated sulphate of potash or
10 grams in the case of kainit or other low-grade
salts) shall be boiled with 300 cubic centimetres of
water in a half-litre flask or beaker. The solution
shall be acidified with hydrochloric acid, and
barium chloride solution shall be cautiously added,
drop by drop, to the boiling solution until the sul-
phuric acid is completely precipitated. The liquid
(without filtration) shall be cooled, made up to
500 cubic centimetres, and filtered. Of the filtrate,
25 or 50 cubic centimetres shall be made alkaline
with ammonia and treated with excess of a sat-
rated solution of ammonium carbonate, followed by
a few drops of a saturated solution of ammonium
oxalate to precipitate excess of barium. The pre-
cipitate shall be filtered off and washed, and the
filtrate and washings shall be evaporated to dryness
and ignited carefully below red heat until all volatile
matter is driven off. The residue shall be digested
with hot water, filtered, and washed with hot water,
and the potash determined in the filtrate by
the perchloric acid method prescribed below in
clause (d). If the solution contains phosphates,
iron, manganese, or other substances that would
interfere with the determination of potash, the
method prescribed in clause (c) of this paragraph
is to be used instead of the method prescribed in
clause (b).

(c) Potash in mixed fertilizers:—

Ten grams of the sample shall be boiled with 300
cubic centimetres of water, and filtered. The
residue shall be washed on the filter with
hot water and the solution when cold
shall be made up to 500 cubic centimetres.
Of the filtrate from 25 to 100 cubic centimetres
shall be diluted and acidified with hydrochloric
acid and barium chloride solution shall be cau-
tiously added, drop by drop, to the boiling solution
until the sulphuric acid is completely precipitated.
The solution shall be filtered while hot and the
precipitate washed until free from chlorides. The
solution shall be made alkaline with ammonia and
the excess of barium precipitated with a saturated
solution of ammonium carbonate, followed by a
few drops of a saturated solution of ammonium
oxalate. The precipitate shall be filtered off and
washed, and the solution shall then be evaporated
to dryness and ignited carefully below red heat
until all volatile matter is driven off. The residue
shall be digested with hot water, filtered, and
washed with hot water, and the potash determined
in the filtrate by the perchloric acid method pre-
scribed below in clause (d).

(d) Perchloric acid method:—

To the solution obtained as above described in
clause (a), (b), or (c) of this paragraph and placed
in a small glass or porcelain basin, 3 to 6 cubic
centimetres of a 20 per cent. solution of perchloric
acid (specific gravity 1·125) shall be added. The
basin shall be placed on a hot plate or sand bath
and the contents evaporated until white fumes are
copiously evolved. The precipitate shall be re-
dissolved in hot water, a few drops of perchloric
acid solution added, and the whole concentrated
again to the fuming stage. After cooling, the
residue in the basin shall be thoroughly stirred
with 20 cubic centimetres of alcohol of specific
gravity 0·816 to 0·812 (95 to 96 per cent. of alcohol
by volume). The precipitate shall be allowed to
settle for half an hour, and the clear liquid shall be
poured through a weighed or counterpoised filter
paper, or through a gooch crucible, draining the
precipitate as completely as possible from the
liquid before adding the washing solution. The
precipitate shall be washed by decantation with
alcohol (as above) saturated with potassium per-
chlorate at the temperature at which it is used,
pouring the washings through the paper or gooch
crucible on which the whole of the precipitate
is finally collected, dried at 100° C., and weighed.
The precipitate is to be regarded as KCIO₄ and is to be
calculated to its equivalent as K₂O.

LIMITS OF ERROR.

10. (1) For the purposes of the provisions of the Act con-
    cerning the effect, as a warranty, of the statements made in
    the invoice certificate of a fertilizer respecting the percentage
    of any fertilizing ingredient, the limits of error shall be as
    under, the figures given representing percentages of the whole
    bulk :—

• That is, soluble in a solution of citric acid of prescribed strength.

(2) The limits of error in the statement of percentage of
fineness of grinding shall be 2·5 per cent.

Fineness of Grinding of certain Fertilizers to be stated.

11. The fineness of grinding shall be stated in the case of
    the following fertilizers:—

Basic slag.

Ground raw rock phosphate.

Standards of Fineness of certain Fertilizers.

12. The following fertilizers shall be ground to a state of
    fineness so that not less than 80 parts per centum by weight
    shall pass through a sieve having the standard wire mesh No.
    100 E of Amandus Kahl, Hamburgh :—

Basic slag.

Ground raw rock phosphate.

Provided that in so far as ground raw rock phosphate is
concerned the provisions of this clause shall be suspended
until the 1st day of September, 1929.

Fineness of Grinding.

13. Where it is provided by these regulations that the fine-
    ness of grinding of the fertilizer or any component part of
    such fertilizer must be disclosed in the deposited statement
    and invoice certificate this will mean that the vendor must
    state the percentage of such fertilizer that will pass through
    a sieve having the standard wire mesh No. 100 E of Amandus
    Kahl, Hamburgh.

Citric Acid Solvent.

14. When in any deposited statement or in any invoice
    certificate it is specified that a certain percentage of the phos-
    phoric acid contained in the fertilizer is citric soluble or
    soluble in citric acid, this shall be taken to mean that it is
    capable of being dissolved to the extent of such percentage
    when 5 grams of the fertilizer and 500 cubic centimetres of
    water containing 10 grams of pure crystallized citric acid, or
    alternatively when 5 grams of the fertilizer, moistened with
    5 cubic centimetres of alcohol or methylated spirit, and 495
    cubic centimetres of water containing 10 grams of pure
    crystallized citric acid, are continuously agitated in a flask
    or bottle of about one litre capacity for a period of thirty
    minutes at a temperature of approximately 65° F.

ANALYST NOT TO BE INTERESTED IN ANY BUSINESS CON-
NECTED WITH THE SALE OF FERTILIZERS.

15. No person while holding the office of Analyst under the
    Act shall engage or be interested in any trade or business
    connected with the manufacture, sale, or importation of
    materials used for fertilizing the soil.