Question

Assume that you have just been hired to work for a chemical company. Your first job is to collect a sample from a railroad boxcar full of of soda ash for chemical analysis. Look up in the ASTM procedure in the lilbrary and quote the procedure. It is one sentence. Give full literature citation.

Answer 1

Literature: ASTM E359 - 17 Standard Test Methods for Analysis of Soda Ash

We wish to analyse the sample for soda ash (sodium carbonate)

We can use the following method

1) we can use titrametric method. The method starts by converting sodium Bicarbonate to carbonate by adding it in excess of NaOH, followed by precipitation with barium chloride solutions. The excess NaOH left is back-titrated with a standard acid (HCl) solution and we use pH meter for determination of exact end point.

Procedure

a) weigh an equal weight of sample and a primary standard sodium carbonate.

b) take 200 mL of 120g/ L of BaCl2 solution in a beaker.

c) adjust the pH of solution by adding NaOH or HCl as desired using a pH meter,

d) Take 150mL of water in a beaker and add 5mL of 0.1N NaOH. Check the purity of water for any dissolved CO2.

e) to the above beaker containing NaOH add the weighed amount of sample.

f) Stir the mixture with the help of magnetic stirrer.

g) continue stirring and add the 200 mL of neutralized BaCl2 with the help of pipet

h) Now use pH meter electrodes and measure the pH of solution and tirate against 0.1N HCl. Keep stirring. The end point will be observed at pH =8.8. Record the volume of HCl used.

i) Calcualte % of Na2CO3 as

Where

B= volume of HCl used for standard Na2CO3

A= volume of HCl used for sample

N = normality

W= amount of sample taken in grams