J.P. SELECTA PRO-NITRO A Instruction Manual page 45

MANUAL DE INSTRUCCIONES
START
Boric.....60 ml
NaOH......15 ml
Norm......0.250
«OPERATION MENU»
Analysis Nr: XXXXX
DD/MM/YY hh/mm/ss
HCl(ml)... 00.000
N(mg)..... 000.000
«RESULTS SCREEN»
J
.P. SELECTA s.a.u.
CODIGO 80189 REV E
Prime: It gives order to the digital dispenser to dispense continuously until the key
«ESC» be pressed. This function is used to prime the dispensing tubing or for its
cleaning.
5.1.3 «OPERATION» Menu
This menu allows programming the analysis parameters and initiating the analysis.
By selecting the «START», the analysis is initiated with the parameters that are
shown on the display.
The parameters can be modified pointing it by the arrow keys and pressing «EN-
TER».
Analysis parameters:
«Boric»: Sets the fixative solution volume to be dispensed on the collector. Value
factory set is 55 ml and, usually, it will never be modified.
«NaOH»: Sets the NaOH to be dispensed on the sample tube. Usually a volume
from 50 to 75 ml should be used for sample analysis.
Note: This volume depends on the sulphuric acid volume used on the digestion
step.
«Norm.»: Set the titration reagent concentration (Normality) (usually HCl 0.25N).
Values from 0.01N to 1N could be set.
The parameters programmed remain stored on the unit for later use.
Note: The precision of the results are affected directly by the precision of the acid
normality used for titration. This is a common cause of error, because, after
some time, opened bottles tend to increase its normality.
Also, often there are errors in concentration calculation to prepare the acid for
titration.
Check often the real value of the normality and update its value on the analyser.
On selecting «START» the distillation & titration are initiated.
On this distillation & titration process, four steps could be identified:
1. Fixative solution (Boric) and NaOH dispensing. The display shows the reagent
that is being dispensed.
2. Distillation: for 1.5 minutes the sample is distilled without titration.
3. Distillation & titration: The digital dispenser starts the distilled titration until the
colour change is detected.
4. Titration: Just in case that distillation was very long (sample with high nitrogen
contents o titration reagent with low Normality) the distillation is stopped but titra-
tion continues.
During the steps 2, 3 and 4 the display shows the «RESULTS SCREEN» where the
consumed HCl volume (ml) and detected nitrogen (mg) is indicated.
Autovía A-2 Km 585.1 Abrera 08630 (Barcelona) España
e-mail: selecta@jpselecta.es - website: http://www.jpselecta.es
12/2020 Pag.: 45
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