FAQ's Model 926 Chloride Analyser
Question 1 - What does the "mg%" button do?
Answer 1 - Firstly the relationship between the chloride and salt content
The Atomic weight of Na = 22.98 Cl = 35.45
so the molecular weight of Na Cl is 58.43
so to convert from Cl to NaCl we multiply by 58.5/35.45 = 1.6482.
This is the factor which is used when you press the "mg%" button
A reading of 200 on the display for chloride is converted by pressing the mg% button to 200 x 1.6482 = 329 mg/I NaCl = 033 mg % (mg per 100 gms water) we then multiply by the 100: 1 dilution factor = 3300 mg % or 3.3 %. (gms per 100 gms water) which is the concentration in % of the original sample before diluting 1:100
Therefore the mg% button on the model 926 only works if the original sample is diluted 1:100.
Question 2 - How can the Model 926S measure the concentration of chloride with a 20 µl aliquot and a 100 µl aliquot from the same sample and get the same answer? Surely the amount of chloride added is 5 times greater in the latter aliquot?
Answer 2 - Yes there is 5 times less chloride added in 20 µl sample than in 100 µl but when the "20µl" button is pressed the Model 926S adjusts the constant current to 20% of the value it uses for a 100 µl sample.
The rate of formation of silver is only 20% and so the instrument still takes the same time to react with the smaller sample of chloride and thus it displays the same concentration. The exact 20% rate is calibrated at the factory at the same time as the default 100 µl rate.
Question 3 - How long does an anode last (92511003 contains 3 anodes).
Answer 3 - The Model 926 works by generating silver ions at the anode. These dissolve in the acid buffer and react with any chloride ions present from the sample/standard.
The rate of generation of the silver is governed by the electrochemical equivalency. This states that 1 Faraday (96500 coulombs of current will release 1 mole silver (107.87 grams). This is also exactly equivalent to 1 mole chloride (35.45 grams).
Each anode weighs 1.4 grams and a third of this is lost when the anode is finished
Mass Ag = 1.4/3 = 0.467 gms
Mass Cl = 0.467/107.87 x 35.45 = 0.1534 gms chloride
So, if 50 samples a day each containing 200 mg/l chloride and 0.5 mls aliquots are used
1 day = 50 x 0.5 x 200/1000000 grams Cl = 0.005 grams
Therefore 1 electrode will last 0.1534/0.005 days = 30.68 or just about 1 month.
Question 4 - Will Active Salt Software work with the M926S Chloride Analyser
Answer 4 - The Model 926S Chloride Analyser measures Chloride concentration in mmol/l and therefore the data generated is not suitable for use with Active Salt which performs a calculation based on the premise the Chloride data entered is in units of mg/l.
Question 5 - Can I collect data from more than one M926 with Active Salt?
Answer 5 - Only one copy of Active Salt software may be hosted on a PC but there is provision to run two instances of Active Salt; each collecting data from one M926 and one RS232 enabled balance.
So with one PC it is possible to collect data from two Chloride Analysers and two balances using one copy of Active Salt (from revision 1.07 onwards).
Question 6 - Can I run Active Salt software on a 64Bit Windows system?
Answer 6 - Yes the software will run OK on 64Bit Systems.
You will get an error message when the software is installed. Just choose "Continue" and the software will load. When finished the Acive Salt icon will appear on the PC or LapTop's DeskTop. Right click the application, select compatibility mode and check the option to always run as an administrator.
You only need do this once and the settings will be remembered so the program will then open up without error next time you use it.