MANUAL DE INSTRUCCIONES CODIGO 80188 REV E
Jun/2018
(Sujetas a modificaciones sin previo aviso) Pag.: 45
J
.P. SELECTA s.a.u.
Autovía A-2 Km 585.1 Abrera 08630 (Barcelona) España
Tel 34 937 700 877 Fax 34 937 702 362
e-mail: [email protected] - website: http://www.jpselecta.es
The volume consumption of HCl (Vol
-
HCl
) on the titration can be forecasted
from the expression:
P
1
(mg) = 14 x Vol
HCl
(ml)
x N
HCl
thus we obtain that HCl must be:
Vol
HCl
(ml) = 14 /[ P
1
(mg) x N
HCl
]
8.3 Blank test
This checking must be run on each batch in order to quantify the absence of am-
monia on the reagents.
It consists on distilling and titrating a sample of 25ml of distilled water.
Add 15ml of NaOH on the distillation.
Run some blank tests in order to get a constant value of blank. If this value is
repeated it could be subtracted from the detected Nitrogen.
8.2 Checking Nitrogen Recovery
This checking is widely used to certify that the unit works properly.
Run some of these test for training purposes before starting to analyse valuable
samples, until the operator will be familiar with the unit.
It consists to prepare some samples that have a known Nitrogen content. It is
distilled, titrated and the nitrogen detected is calculated.
The rate (%) of nitrogen detected versus the sample Nitrogen content gives us the
Nitrogen Recovery
.
To allow this checking, a 100gr ammonia sulphate flask is delivered together with
the distiller.
• Weight near 100mg (50mg reagent 0.1N) of ammonia sulphate. The exact
weight will be P
0
• The exact quantity of Nitrogen is: P
1
(mg) = P
0
x 0,212
• Add around 25ml of H
2
O
• Distillate adding 15ml of NaOH
• Use HCl 0.25N (0.1N) as a titration reagent.
• Once distilling and titration (see 6.5) are finished, calculate the detected nitro
-
gen (mg) : P
2
• The recovery is calculated:
R(%) = P
2
/ P
1
*100
• Acceptable values are from 99.0 to 101.5 %.
Note:
Some literature sets that the acceptable values for recovery must be above
99.5%. To get this result you must work with high precision and use reagents with
high purity degree.
How many ammonia sulphate
must I put on the test sample?
The HCl volume (Vol
HCl
) for a quick
analisys must be between 6 and 12
ml.
From the expresion:
P
1
(mg) = 14 x Vol
HCl
(ml)
x N
HCl
We arrange it as:
P
0
(mg) =
14 x Vol
HCl
(ml) x N
HCl
0.212
And yields the table:
Normality
Sample amount
Sufate ammon.
0,05
20 ... 40 mg
0,1
40 ... 90 mg
0,25
100 ... 200 mg
0,5
200 ... 400 mg
8.1.6 Checking sample tube empty function
Place a MACRO sample tube with around 100ml distilled water.
Select MANUAL mode. Press «EMPTY/STOP». This starts the pump to empty the
sample tube to the waste output.
