Foreword
Appendix A of this standard is normative, Appendix B is informative.

National Food Safety Standard
Feed additive—Zinc sulfate
1     Scope
This standard applies to feed additive zinc sulfate produced by the reaction of sulfate and zinc oxide or obtained by sphalerite roasting, and then purified by acid leaching.
2     Normative References
The following documents for the applications are more essential. For dated references，the note-date version applies this document .For undated references, the latest version applies this document.
3     Formula and relative molecular mass
3.1  Formula
Zinc sulfate monohydrate: ZnSO₄·H₂O
Zinc sulfate heptahydrate: ZnSO₄·7H₂O
3.2  Relative molecular mass
Zinc sulfate monohydrate relative molecular mass: 179.49 (According to 2007 international relative atomic mass)
Zinc sulfate heptahydrate relative molecular mass: 287.58 (According to 2007 international relative atomic mass)
4     Technical Requirements
4.1  Sensory requirements: must meet the requirements of Table 1
Table 1 Sensory requirements

Project	Requirements	Test Methods
Color	White or Colorless
Organization of the state	Zinc sulfate heptahydrate is of crystals or granules. Zinc sulfate monohydrate is of flowing or coarse powder.	Take the right amount of the sample, then place it in a beaker of 50ml and observe the color and texture in natural light.

 
4.2  Physical indicators: must meet the requirements of Table 2
Table .2 Physical indicators:

Project		Indicators		Test methods
		Zinc sulfate monohydrate	Zinc sulfate heptahydrate
Zinc sulfate	In total zinc sulfate monohydrate, w/%	99.0~100.5	-	A.4 in Appendix A
	In total Zinc sulfate heptahydrate, w/%	-	99.0~108.7
Acidity		Through tests		A.5 in Appendix A
Alkali metal and alkaline earth metal salts, w/%		0.50		A.6 in Appendix A
Cadmium (Cd)/(mg/kg)		2		A.7 in Appendix A
Lead (Pb) /(mg/kg)		4		A.8 in Appendix A
Mercury (Hg) /(mg/kg)		1		A.9 in Appendix A
Selenium (Se) /(mg/kg)		30		A.10 in Appendix A
Arsenic (As) /(mg/kg)		3		A.11 in Appendix A

 

Appendix A
(Normative Appendix)
Test Methods
A1   Alert
Part of the standard test reagents used are toxic or corrosive .The operation needs to be careful! If it is spilled on the skin, one should immediately wash with water. Severe cases should be treated immediately. When using volatile acid, it need to be operated in the hood.
A.2  General Provisions
The standard reagents and water, without indicating its requirements, both refer to analytical reagent and 3rd level water according to GB/T 6682-2008. The standard solution, the standard solution of the impurities, test formulations and the desired product are all prepared according to HG/T 3696.1, HG/T 3696.2, HG/T 3696.3.
A.3  Identification Test
A.3.1      Identification of zinc ions
A.3 1.1   Reagents and materials
A.3.1.1.1       Chloroform
A.3.1.1.2       Acetic acid solution: 1+10
A.3.1.1.3       Sodium sulfate solution: 250g/L
A.3.1.1.4       Diphenylthiocarbazone solution: 1+100
A.3.1.2   Analysis step
0.2g sample was weighed and dissolved in 5ml of water. Pipette 1ml test solution, adjusted Ph value to 4-5 with acetic acid solution. Then added 2 drops of sodium sulfate solution, some drops of diphenylthiocarbazone solution and 1ml chloroform. After shaking, the organic layer was purple.
A.3.2      Identification sulfate
A.3.2.1   Reagents and materials
A.3.2.1.1       Barium chloride solution: 50g/L
A.3.2.1.2       Hydrochloric acid solution: 1+1
A.3.2.2   Analysis step
1g sample was weighed and dissolved in water. Add some drops of barium chloride solution, and then produce the white precipitate. The precipitate is insoluble in hydrochloric acid solution.
A.4  Determination of zinc sulfate
A.4.1      Method Summary
The zinc sulfate is dissolved in sulfuric acid solution. Then add some amount of water and ammonium fluoride solution, thioureas, ascorbic acid as masking agent. The Ph value is adjusted to 5-6 by acetic acid - sodium acetate solution. The disodium edetate standard solution is used as the titration. The titration end is indicated as the solution color becomes bright yellow from purple with the xylenol orange indicator .
A.4.2      Reagents and materials
A.4.2.1   Ascorbic acid
A.4.2.2   Thiourea solution: 200g/L
A.4.2.3   Ammonium fluoride solution: 200g/L
A.4.2.4   Sulfuric acid solution：1+1
A.4.2.5   Acetic acid - sodium acetate buffer solution：Ph≈5.5
A.4.2.6   The disodium edetate standard solution: c (EDTA) =0.05mol/L
A.4.2.7   The xylenol orange indicator solution: 2g/L, the using period is no more than 1 week.
A.4.3      Analysis step
Weigh 0.2g of the zinc sulfate monohydrate or 0.3g of the zinc sulfate heptahydrate, accurate to 0.0002g. Put it to a erlenmeyer flask of 250ml .Drop two drops of Sulfuric acid solution to dissolve, and add 50ml of water，10ml of Ammonium fluoride solution, 2.5ml of thiourea solution, 0.2g of ascorbic acid. After shaking it uniformly, add 15ml of acetic acid - sodium acetate buffer solution and 3 drops of the xylenol orange indicator. The titration end is indicated as the solution color becomes bright yellow from red with the xylenol orange indicator. At the same time, do the blank test.
In the blank test ,they are the same as the determined sample in the reagents species, the amount and other operating steps,but no sample.
A.4.4      Results
Zinc sulfate content is noted with zinc sulfate monohydrate or Zinc sulfate heptahydrate mass fraction ω1, the value is showed by %, calculated by Formula (A1):

Where:
C---the value of disodium edetate standard titration solution concentration, the unit is mol/L;
V--consumed disodium edetate standard titration solution volume in titration ，the unit is ml;
V0--consumed disodium edetate standard titration solution volume in blank titration, the unit is ml;
m----the quality of the sample, the unit is g.
M---Zinc sulfate molar mass, the unit is g/mol. The main content noted by Zinc sulphate monohydrate mass fraction, M is 179.5; the main content noted by zinc sulfate heptahydrate mass fraction, M is 287.6.
Taking the arithmetic mean value of parallel determination as measurement results. The parallel determination results absolute difference is not more than 0.2%.
A.5  Determination of acidity
A.5.1      Reagents and materials
A.5.1.1   Water without carbon dioxide
A.5.1.2   Methyl orange indicator solution
A.5.2      Analysis steps
Weigh 1g of the sample, dissolve it in freshly prepared 20ml of the water without carbon dioxide, then drop 3 drops of methyl orange indicator solution. The solution can’t occur pink.
A.6  Determination of alkali metal and alkaline earth metal salts
A.6.1      Reagents and materials
A.6.1.1   Ammonia
A.6.1.2   Hydrogen sulfide, prepare it when used.
A.6.2      Analysis steps
Weigh 0.2g of the sample, accurate to 0.01g. Put it to a erlenmeyer flask of 250ml .Add 150ml of water, 15ml of ammonium, then shake it and dilute it to the mark with water. Remove 250 ml of the solution, and fully pass into hydrogen sulfide, then stand it for several minutes. The supernatant is filtered with filter paper, the small amount of the filtrate is discarded. Pipette 100ml of the filtration solution to the crucible with constant quality , add 0.5 ml of sulfuric acid, evaporate to the dryness, and burn it till the quality is constant at 700℃.
A.6.3      Results
Alkali metal and alkaline earth metal salts content is noted with the mass fraction ω2, the value is showed by %, calculated by Formula (A.2):

Where:
m1----the quality of the residue, the unit is g;
m---the quality of the test sample, the unit is g;
Take the arithmetic mean value of parallel determination as the measurement results. The parallel determination results absolute difference is not more than 0.01%.
A.7  Determination of cadmium
Weigh 10.00g+0.01g of the sample , place it to a 150ml of beaker，add 40ml of water to dissolved and remove it completely to a flask of 100ml. At the same time, prepare the reagent blank solution. The following steps are according to GB/T 5009.15---2003.
A.8  Determination of lead
Weigh 5.00g+0.01g of the sample, place it to a beaker of 150ml ,add 20ml of water and 1ml of nitric acid solution (1+1) to dissolved. After evaporating to be dry with the water bath, dissolve it in 25ml of water. The following steps are according to GB/T 5009.12---2010.
A.9  Determination of mercury
A.9.1      Reagents and materials
A.9.1.1   Hydrochloric acid solution: 1+99
A.9.1.2   Iodine solution: 2.5g/L
A.9.1.3   Stannous hydrochloric acid solution: weigh 25g of stannous and dissolve it in 50ml of hot concentrated hydrochloric acid. Move it to a 250ml of flask after cooling and dilute it to the mark with water.
A.9.1.4   Stock solution of mercury standard solution: 1mL of the solution contains 0.1mg of mercury.
Preparation: pipette 10ml of the standard mercury solution according to HG/T 3696.2, place it to a 100ml of the flask, dilute it to the mark and shake it.
A.9.1.5   Mercury standard solution: 1ml of the solution contains 0.001mg of mercury.
Preparation: pipette 1ml of the standard mercury solution according to HG/T 3696.2, place it to a flask of 100ml, dilute it to the mark and shake it. The solution is prepared timely when using.
A.9.2      Instruments and equipment
Mercury analyzer or atomic absorption spectrophotometer: With a mercury hollow cathode lamp, cold atomic vapor generating device, digestion.
A.9.3      Analysis steps
A.9.3.1   Preparation of test solutions
Weigh 4.00+0.01g of the sample, place it to a 100ml of beaker, dissolve it in the water, remove to a flask of 50ml completely, dilute it to the mark, and shake it.
A.9.3.2   Work curve plotted
Take five flasks of 50ml, add the standard mercury solution respectively according to Tab A.1, dilute it to the mark and shake it.
Tab A.1 Mercury Working curve

No. separatory funnel	1a	2	3	4	5
The volume of the standard mercury solution /mL	0	2.00	4.00	6.00	10.00
The quality of mercury solution /mg	0	0.002	0.004	0.006	0.010
a Reagent blank solution

Place the mercury curve solution to the instrument mercury vapor generator restore bottle ,add 1ml of stannous solution respectively, cover the bottle tightly, access the carrier gas and read the displayed absorbance value from the instrument. Minus the curve solution absorbance value with the reagent blank solution absorbance value, draw working curve with the quality of mercury in solution as the abscissa, with the corresponding absorption value as the vertical.
A.9.3.3   Determination of the sample solution
The test solution is operated according to A.9.3.2 “add 1ml of stannous”, till to measure the absorbance of the solution. The mercury-containing waste water treatment is according to appendix B.
A.9.4      Results
The mercury content is noted by mercury mass fraction ω3, shown as mg/kg, calculated as formula (A.3):

Where:
m1--the quality of mercury in the test solution from the working curve, the unit is mg;
m--the quality of the sample, the unit is g.
Take the arithmetic mean value of parallel determination as measurement results. The parallel determination results absolute difference is not more than 0.5mg/kg.
A.10       Determination of Selenium
Weigh 5.00g+0.01g of the sample , place it to a 150ml of beaker，add 20ml of water and 1ml of nitric acid solution(1+1) to dissolve,then evaporate to be dry with the water bath .The following are determined according to GB/T 5009.93---2010 hydride atomic fluorescence spectrometry.
A.11              Determination of Arsenic
Weigh 5.00g±0.01g of the sample, place it to an erlenmeyer flask, moist with water, add some hydrochloric acid to the neutral state, add 5ml of hydrochloric acid to the overdose, and shake it. Pipette 2ml of arsenic standard solution as the standard, place it to another erlenmeyer flask. Add 5ml of hydrochloric acid (1+3) respectively . The determining is according to 6.2 in GB/T 5009.76---2003 or chapter 11.
Diethyl dithiocarbamate silver assay is as the Arbitration Act.
Appendix B
(Information Appendix)
Mercury-containing waste water treatment
Collect the mercury-containing waste water to a container of 50L. When the waste water reaches about 40L, add 400ml of 400g/L sodium hydroxide solution, 100g of Na₂S·9H₂O and shake it. Add 400ml of 30% hydrogen peroxide solution in 10 minutes, and mix them completely. The supernatant is discharged to the waste water after 24h. The precipitate is transferred to another container. The recovery of mercury is handled by hand.

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