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I've done the first treatment with concentrated nitric acid but I only let it reflux for about 2 hours rather than the planned 24 hours. Pictures: http://i.imgur.com/X9rkgyP.jpg http://i.imgur.com/yBoIMC5.jpg http://i.imgur.com/oqg2XJc.jpg There was too much NO2 gas and even with two...

The setup will be condenser - tubing - drying tube - y or t connector - air supply in one connection - other connection with tubing to scrubbers. Wouldn't an air flow into my system, cause the gases to return backwards through the drying tube and into the condenser and reaction flask avoiding...

Based on the glassware I could find this is the setup I came up with: 1L 3-necked round bottomed flask (I couldn't find a regular 1L round bottomed flask) connected to an Allihn condenser, water in the bottom and out the top. Drying tube attached to one of the necks of the flask since you...

My final purpose is to introduce basic sites into my carbon just as you said. I am more or less going to follow the exact procedure listed in the article (just scaling up) but the use of benzene (or toluene) as a solvent is an issue as I explained. You seem to have a vast amount of knowledge and...

So without a stopper this means that I will be allowing any vapors escape my system and at the same time my liquid quantities will reduce. How do I properly control the mixtures and make sure it will not dry out while it's left overnight? It's great that you brought up cleanup and waste...

I will be treating carbon in 3 steps under reflux and I would really appreciate some suggestions, tips and advice on getting a proper and SAFE setup in the lab. I have at my disposal a fume hood and standard laboratory glassware. Treatment 1: 20g carbon treated with 100mL 65% Nitric Acid under...

This is exactly what I meant by back-titration. I would add different amount of HCl depending on the initial solution. So for example I will add 20ml of HCl to NaOH while I would add 30ml of HCl to Na2CO3 to ensure complete reaction because 2 moles of acid required to react with 1 mole of sodium...

Typically the time allowed for the carbon to remain in contact with the solutions is 24 hours and the maximum I've read is 72 hours. This is to allow enough time for the surface groups to get neutralized and from my experience to ensure that there is a measurable amount of titrant required to...

I standardized my NaOH solution with KHP and the concentration was 0.047M rather than the intended 0.05M. Is it acceptable to use the (now standardized) 0.047M NaOH solution to standardize my HCl solution. Then using the HCl solution to standardize the NaHCO3 and Na2CO3 solutions? A bit of...

For all the bases I used 99% or higher purity pellets (in the case of NaOH) or powder (NaHCO3 and Na2CO3). I calculated the mass required to achieve 0.05M and dissolved in the corresponding volume of distilled water I need in a volumetric flask.

Thank you. As you have noticed, even though Boehm titration is supposed to be a standard method, both papers have variations. Plus it seems they suggest a direct titration rather than a back-titration. I've tried performing a direct titration but it was difficult to get the same or almost the...

I'll double-check my calculations. As for my procedure I followed the general Boehm titration procedure as mentioned in this journal article: Standardization of the Boehm titration Part I CO2 expulsion and endpoint determination, S. L. Goertzen et. al, Carbon 48 (2010) 1252-1261. I'll...

I avoided the negative by subtracting the NaHCO3 titration from the Na2CO3 titration. I've been trying to figure it out, I'm not sure whether it's just my tiredness or do the numbers really don't make sense. You do agree that the results don't make sense, right?

I'm posting this here because I did not get much help from the Chemistry section. Please read further. Anyone familiar with the Boehm titration procedure and calculations? I've done the titrations based on what I was able to gather from literature and the calculations but the results don't...

Maybe someone can help me workout the calculations and if the science checks out, this is what I've gotten so far: After mixing separate batches of carbon with NaOH, NaHCO3 and Na2CO3 I will titrate directly the solution with HCl. In the case of NaOH titrated with HCl, at equilibrium moles...

DrDu thank you for your reply, however, during my search I also found the articles you mentioned but I could only get a copy of the second article from the Carbon journal which unfortunately doesn't provide details of the method. The first article, which I believe describes the titration method...

There is too much difference in literature regarding the procedure for Boehm Titration and my efforts to find the original article which describes the method developed by Boehm himself has not been fruitful. Boehm titration is an acid-base titration method which is used to determine the...

Is it frowned upon to use mass rather than volumes to transfer liquids?

I haven't done this before but what do you think about measuring the density of my stock solution and calculating the mass required to be diluted?

I've calculated how much of stock solution I would need to make lower concentration solutions and looking at the volumes and glassware capacities at my disposal I would need to transfer liquids several times to get the required amount before diluting which would add errors. Would it be better...

Thank you. I'm just having one of those nights. One last thing. Is there any other way besides using a burette to accurately transfer large liquid volumes between 100-400mL?

You have an excellent point. Now here's something else that is weird. Lets say I make a 250mL stock solution of xylene with a concentration of 190mg/L (slightly lower than the max solubility!). If I want to make a 500mL solution with a concentration of 100mg/L using the stock solution. Using...

I think I figured out that I should be looking at the concentration of the solution rather than the mass of the analyte. After a bit of number crunching this is what I got: If I add 57µL which is equivalent to 49.248mg of xylene and make it up to 250mL of water I get a solution...

I'm making a stock solution of xylene in water. The solubility of xylene in water is 200 mg/L (Andrews and Keefer 1949). The density of xylene is 864 mg/mL. Making 1 L stock solution is too much and a waste. 0.23mL (or 230µL) of xylene is equivalent to 198.72mg. To make the stock...

Thank you again JohnRC. I'll answer your questions below in blue.

Thank you very much JohnRC. Thanks to you I was able to determine that the issue was with my carbons and my equipment is also to blame. But I still have some queries regarding adsorption experiments. Since I'm still at the early stages of my experiments, I first must determine the time it...

This is more than excellent. Thank you for the great idea. I've done liquid liquid extraction a long time ago and it's a bit fuzzy in my head. Just a few questions in regards to it. Say I use water as my solvent to prepare the benzene solution for adsorption and then use something like hexane...

Thanks for the reply JohnRC I did not do that, I will give it a try. Do you mean, using the the carbon after it has been placed in the ethanol solvent (no benzene) into a solution which has benzene for the adsorption? I realize ethanol is not ideal (nor is methanol) but I have very few...

Adsorption of Benzene using Activated Carbon - Increase in concentration!? I'm not quite sure where to post but here it goes. I'm performing an adsorption experiment of benzene from solution using commercial activated carbon. It is expected that the concentration of benzene would decrease...

1) i.e having replicates of each batch/experimental solution? 2) I did filter my solutions before adding them to the cuvette 3) Are there any other non-standard/conventional methods? What about GC-MS?

Each chemical (Benzene, Toluene, Xylene) has a lambda max which gives the maximum absorbance. I measured the absorbance at these wavelengths to get the highest absorbance. Edit: So for Benzene literature reports a lambda max of 255nm, 262nm for Toluene and 265nm for Xylene. I also confirmed...

I am back with my results from my adsorption experiment but they don't make any sense and are not logical (to me at least)! I have uploaded my results as a pdf file on google docs, I hope someone can have a look https://docs.google.com/open?id=0B8vof1fhvsO6Mzd3UE5QY2dKMFk Let me explain my...

This is a follow-up question on my progress. I was able to obtain 2 quartz cuvettes (10.00mm) and so far the absorbance measurements giving me consistent results with my standard solutions. However, once I reach my maximum concentration solution of 450ppm the absorbance given my the UV-Vis...

What defines the sensitivity? The chemicals are high grade purity, with methanol at 99.99%, toluene and xylene at 99.44%.

I asked a colleague who has been using the UV-Vis in the lab and he told me that I should prepare different standard solutions of varying concentrations. My initial adsorption experiment solutions are at 200ppm and 400ppm so according to him I should first prepare standards at 50ppm, 100ppm...

I have been conducting liquid phase adsorption experiments of xylene and toluene using activated carbon. I made solutions at 2 concentrations (200ppm and 400ppm) of individual components of toluene and xylene in methanol, as a solvent. Initially, the plan was to use Gas Chromatography to...

Yes, I want to dilute it in water. I don't require very high accuracy but I would like to get a proper solution for my experimental study (adsorption). Can you please elaborate further on "micropipette, volume/mass/density" ?

But I'm working with liquid toluene, so using a balance to measure mass would be bring inaccuracy to the measurement. Also how would I take into account the 99.5% spec given?

It's been a while since I last worked in the lab and I have forgotten some of the techniques in preparing solutions, especially when dealing with liquid solutes. I'm trying to make solution of toluene of low concentrations in the ppm levels. The specifications as shown here...

Homework Statement I'm trying to calculate the saturation pressure and the densities of a liquid and vapor using an equation of state. I figured out how to do it and know how to proceed except that I don't understand Maxwell's Principle which is stated in number 2 below. Homework...

1. Homework Statement Iron sample with dimensions 10mm x 20mm x 2mm is exposed to a corrosive environment (neglect thickness for surface area). Both sides of the sample are exposed to corrosive environment. Given http://i.imgur.com/tGRw4.jpg" (a) Calculate corrosion rate mm/y (b)...

Homework Statement Iron sample with dimensions 10mm x 20mm x 2mm is exposed to a corrosive environment (neglect thickness for surface area). Both sides of the sample are exposed to corrosive environment. Given http://i.imgur.com/tGRw4.jpg" (a) Calculate corrosion rate mm/y (b) Calculate...

What I've got so far: dH=[V-T(dV/dT)]dP dU=[V-T(dV/dT)]dP - d(PV) For Entropy: dS=dU/T + (P/T)dV substituting for dU I get: dS=[V/T - (dV/dT)]dP - (1/T)d(PV) + (P/T)dV dS=[V/T - (dV/dT)]dP - (V/T)dP - (P/T)dV + (P/T)dV cancelling the last 2 terms dS=[V/T-(dV/dT)]dP - (V/T)dP By looking at...

I figured it was too good to be true...this is a nightmare! I just got my hands on one of the papers which the book referred to to derive the equations and it looks much more complicated...I could send it to you if you would like to have a look.

This is what I've done earlier for S but after the discussion I think it's wrong dH=TdS+VdP TdS=dH-VdP, substituting for dH and dividing by T dS=[V/T - (dV/dT)]dP - (V/T)dP Using PV=nRT replace V/T by nR/P dS=[nR/P - (dV/dT)]dP - (nR/p)dP , integrating wrt to P S=[nR/P - (dV/dT)]dP - R∑ni*ln...

Gibb's theorem: "a partial molar property (other than volume) of a constituent species in an ideal-gas mixture is equal to the corresponding molar property of the species as a pure ideal gas at the mixture temperature but at a pressure equal to its partial pressure in the mixture" Now just go...

I see, yes...but maybe I don't follow you that well, how would I get the same form of the equation as in the book, equation 3.12...

According to the chapter in the book the equations are for a homogeneous mixture at a fixed composition and temperature and they study effect of pressure and volume, respectively, on enthalpy and entropy. Also it is mentioned that the equations are used to calculate the thermodynamic properties...

H=U+PV U=H-PV dU=dH-d(PV) Then substituting for dH=[V-T(∂V/∂P)]dP and integrating U=∫[V-T(∂V/∂P)]dP - PV + Ʃni*hi I've reached as far as trying to derive the Gibbs Energy equation but I'm stuck again Definition: G=H-TS dG=dH-d(TS), substituting for dH=[V-T(∂V/∂P)]dP Then from...

I'm struggling to derive some thermodynamic equations from this http://my.safaribooksonline.com/book/chemical-engineering/9780132441902/thermodynamic-properties-from-volumetric-data/ch03lev1sec1" [Broken]: Homework Statement I'm trying to derive all the equations from 3.8 to 3.14 for...