Sodium nitrate

SYNONYMS

Chile saltpeter; cubic or soda nitre EMPIRICAL FORMULA  NaNO3

MOLECULAR WEIGHT    85.00

DEFINITION

Sodium nitrate after drying contains not less than 99.0% of NaNO3 and conforms to the following specifications.

DESCRIPTION       

Clear, colorless, odourless, transparent

crystals, or white granules or powder. Deliquescent in moist air.

 

USE

As an antimicrobial preservative and colour fixative in meat, fish and cheese products. Often need In combination with nitrites.

IDENTIFICATION TESTS

 

 

Solubility:   Water:

1 g is soluble in 1.1 ml

 
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Ethanol:

1 g is soluble in 125 ml Glycerol: Slightly soluble Sodium nitrate yields with uranyl zinc acetate TS a golden-yellow precipitate, which forms after several minutes' agitation.

Sodium nitrate yields with uranyl zinc acetate TS a golden-yellow precipitate, which forms after several minutes' agitation.

 

Brownish red fumes are evolved when sodium nitrate is heated with sulfuric acid and metallic copper

PURITY TESTS

 

Loss on drying:            Not more than 2% after drying at 105°C for 4 hours

pH of  a 5% solution

Dissolve 10 g in 200 ml of carbon dioxide- and  ammonia-water, the pH of this solution is between 5.5 and 8.3.

Arsenic

Not more than 3 mg/kg. Lead:               Not more than 10 mg/kg.

Nitrite

Not more than 1000 mg/kg.

 

Dissolve 1 g in 50 ml of carbon dioxide- and ammonia-free water, add 2 drops of dilute ammonia TS, and filter if necessary through paper into a 100-ml volumetric fleck.

Add 10 ml of dilute acetic acid TS, shake  the  mixture,  and  allow  to  stand  for 5  minutes.              Any colour produced is not darker than that of a complete blank to which 1 ml of nitrite standard TS is added.

 

Heavy metals

Not more than 20 mg/kg.

Dissolve 3 g in water and dilute to 30 ml. Adjust 20 ml of this

solution to a pH between 3.0 and 4.0 and dilute with water to 40 ml.

To the remaining 10 ml of sample solution add water to make  35 ml, add         a volume of  standard  lead  TS  equivalent  to  0.02  mg  of  lead  and  adjust to  a  pH  between  3.0  and  4.0  and  dilute to 40 ml.  To each solution add

10 ml of hydrogen sulfide TS, mix, transfer to 50-ml Nessler tubes and observe  after 10 minutes.   The colour of the test solution should be

no darker than that of the solution containing the standard lead solution.

 

ASSAY

 

Weigh 1.000 g of sodium nitrate previously dried at 105°C for 4 hours into the  flask of an  ammonia   distillation apparatus.           Add 10 g of

 

Devarda's Alloya and 25 ml of N

 

sulfuric acid and allow the flask.

to stand, protected from ammonia in the atmosphere, for 1 hour.             

Add 100 ml of a solution of sodium hydroxide (15 in 100), connect the flask to the remainder of the apparatus and distil 100 ml, collecting the distillate under the surface of 25.0 ml of N hydrochloric acid.

 

Rinse the condenser into the receiving flask, add methyl red methylene

 

blue TS and titrate the excess acid with N

 

sodium hydroxide.

 

 

(25-x)

%NaNO3 =                          ×             8.5

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