lanrete

Hi, my laboratory specifies particularly that we use 38% HF as a standard to carry out QC checks on our titration equipment. Anyone knows what is the significance of HF at 38% concentration? It is because i have tons of stock HF at 50% and 49% and thus i would rather use 50% to directly carry out the check than preparing 38% HF from 50% HF then carrying out the QC check. So i want to know what is so special about HF at 38%?

The easiest and cheapest way i know is to use pH paper. There are those out there which can measure to an accuracy of 0.2. Just search the net. If you have the money or resource, get an electronic pH meter.

Hi, i have a bottle of saturated bromine water and the certificate says that the Br amount is 1.5ml and water amount is 100ml. How do i convert this information to Br assay in % value?

What is the method to recover trace Cl ions in hydrofluoric acid? i have tried adding sodium carbonate before evaporation to dryness then recover using ultra pure deionised water. But the result i get is 0 recovery when i measure using ion chromatography. Please help.

Thanks for your input YT2095. I have found that H2SO4 can be isolated by evaporating the sample over a waterbath. This removes both HF and HCl leaving H2SO4 of which the content i can determine with a simple titration with NaOH. Now the problem is how to seperate HF or HCl from the mixture so that i can do another titration to determine the halide acid concentration.

Thanks for trying. I hope some chemistry experts can help me out here.

Hi, in my lab i have a procedure by which excess KNO3 is added to an unknown HF sample and then titrated with NaOH with phenolphthalein as indicator. After this first titration, the sample is then placed in an 80oC waterbath for 1 hour before conducting a 2nd titration with NaOH again with phenolphthalein as indicator. From my manual, it states that this procedure is to determine the HF and H2SiF6 concentration in the sample. So my question is what is the purpose of KNO3 in the procedure? Also can someone deduce the formula of the reaction(s) taking place with KNO3 in this procedure? Thanks

Thats the problem. The molarity and concentration is unknown to me and i need to find it out analytically.

Hi, i have a mixed acid sample of HF+HCl+H2SO4 and i need to find out the individual concentrations of the 3 acids. How can i do so? Urgent help needed. Thanks.