# Borate and rosocyanine

by DaveOB
Tags: borate, rosocyanine
P: 22,714
Not touching anything else, but this

 Quote by DaveOB My research tells me that this should create a 1000 ppm borate solution, so : = 1000 parts per 1000ml = 1 part per 1 ml.
is wrong. Unless you mean something else than you wrote. Concentration is an intensive property and it doesn't depend on the volume. If your solution is 1000 ppm it will be 1000 ppm regardless whether you have 1000 ml or 1 ml. Amount of substance dissolved will be different, but concentration no.
 P: 10 Hi Borek Thanks for the reply. I will try and explain my ( possibly / probably incorrect ) logic. The 'control solution' of 5000ml water, 44 g Borax power and 22ml hydrochloric acid. My thinking was that if this creates a 1000ppm solution, and I then take 1ml of that 1000ppm solution and add it to 250ml water ( b1 ), then b1 will contain 4ppm. ( in my mind it is 1ml or the 1000ppm into 250 ml, so 1 part in 1ml in 250ml water = 4 parts in 1000ml = 4ppm ) Is this logic incorrect ? I used a similar approach when creating a control solution for measuring free chlorine levels and the results have, as far as I can tell, been correct and reasonably accurate so far.
P: 22,714

## Borate and rosocyanine

Looks like your thinking is correct, just the way you name things goes against the standard. ppm mens parts per million, but no chemist will treat "part" as an amount - ppm is meant to be a fraction. Your 1000 ppm solution contains 1000/1000000 of substance in the sample (weight of the substance per weight of sample, or w/w). You can't say "I took 10 parts of 1000/1000000". You can say "I took 1 mL of 1000 ppm solution, and it contained 1000/1000000*1g of the substance" (assuming solution density was that of water - 1 g/mL).
 P: 10 Hi Borek Thanks for the explanation - appreciated. Told you I was "New to chemistry". :) OK. So looks like my control solution and b1 and b2 dilutions ( ? ) are as I calculated ( 1000ppm, 8ppm, 40ppm respectively ) even though I should learn the correct way to get to the right answer, do you have any advice on the core of the problem that I have - that of getting the curcumin to react with the boric acid to form rosocyanine, or do I first need to convert the boric acid to borate ions ? And if this is the case, any suggestions how to achieve this ? Regards Dave
 Admin P: 22,714 Caustic soda is not used to acidify the solution - quite the opposite, it makes the solution alkaline. From what I read this will interfere with the rosacyanine synthesis. I am not convinced you are getting the reaction - seems to me like all your readings are more or less constant. and not concentration dependent.
 P: 10 ok. the light bulb just came on -- now I think it is starting to make sense !! When I first tested, and added curcumin reagent to water with borate solution ( no castic soda ), I saw a flash of red ( assuming rosocyanine ) which disappeared within about half a second. Google told me that rosocyanine would behave like this in an alkaline solution. So I needed to acidify the water. I thought I was doing that with the caustic soda. In reality it was going in the other direction, but adding the caustic soda must have added something / or a reaction to the water that caused the curcumin reagent to turn dark red, making me think that I was on the right track and getting the rosocyanine reaction because of the borates. So what you are saying is that if I replace the caustic soda in my process with an acid ( I have hydrochloric pool acid 30% strength ? ) then I might start getting some predictable / expected results ? Based on this, does the process that I have described seem to be logical, or is there a great big red warning sign that I can't see ? and lastly, a huge big thank you for pointing out the one thing that was not obviously staring me in the face.
P: 10
 Quote by Borek I am not convinced you are getting the reaction - seems to me like all your readings are more or less constant. and not concentration dependent.
Borek - you hit the nail on the head - the reaction I was seeing was not rosocyanine.

video

and about 60 seconds into the video, the author adds curcumin to both an acid and a base ( both with no borates ).
The acid remains the yellow curcumin color, but the base turns a dark red - same as I had.

Now I can go start experimenting with using HCl to acidify the water and see if the curcumin reacts with the borates and forms rosocyanine.
 Admin P: 22,714 Most organic dyes that are weak acids/bases change their color depending on the pH, so it is quite possible that's what you were observing. Can you share a word or two about the color sensor you are using? Chemistry is where I feel comfortable, but I happen to have an Arduino lying on the shelf behind my back and waiting for a better times - sounds like what you are doing (or something similar) could be a nice project to finally start me using the device.
 P: 10 Hi Borek I am using this : sensor and : RGB LED I have a 4 x 4 electrical box with 2 pvc electrical pipe ( conduit ) in a cross shape ( intersecting ). A 15mm glass test tube fits almost perfectly in the 20mm pvc pipe ( 17mm ID ). The vertical pipe sticks out the top of the box, so the test tube can be inserted. Test tube sticks out 15 mm so I cover that with a rubber cap ( like form the bottom of a table leg ) to make it light tight. The horizontal PVC pipe has the LED at one end, covered by a cap, and the color sensor at the other end also covered by a cap. Arduino is in a second 4 x 4 box next to the first box, and an LCD screen and buttons on a 2 x 4 box above that. So the test tube is inserted, the Arduino code controls the LED and shines light thru the tube to the color sensor. I usually calibrate with a tube of sample water, and then add the reagents and do the readings. Results are shown on the LCD. I am using an Adruino Uno 3, and 16 x 2 LCD and a few buttons for menu control, some DS18B20 temperature sensors in the pool pipes, etc. for temperature readings and I would be only too happy to share the code I have if you want it.
 Admin P: 22,714 Thanks - for now it is enough that I know where to look in case I will plan to implement something. I have some ideas bouncing in my skull for over thirty years. I guess that only shows how perfect the vacuum inside must be - no signal attenuation at all.
 P: 10 OK. I think I have some progress now. I checked the pH of the 1000ppm borate solution ( B ) with the pool test strips and it is above 8. So I made a 'carrier solution' ( CS ) of 200ml distilled water and 100ml of hydrochloric acid. The curcumin extract ( CU ) is 40ml acetone + 1 curcumin extract powder capsule. In my test tube, I added 13ml CS, + 2 drops B. Mixed and added 2 drops CU. Then used the sensor to take a green ( 540 nm ) reading. Repeated this process for 4 drops B to 20 drops B, in increments of 2 drops. The numbers started to look promising ( color sensor scale is 0 - 1023 ) : 2 drops : 7.6ppm : 127 4 drops : 15.1 ppm : 125 6 drops : 22.6 ppm : 121 8 drops : 29.8 ppm : 116 10 drops : 37.0 ppm : 110 12 drops : 44.1 ppm : 81 After that point, the numbers started to drift back up again. So I have to assume that one of the following is affecting the reading : After 10 drops, then pH of B ( now more than 0.5ml in 13ml of CS ) is affecting the pH of the 13ml CS in the tube, or The drops of B are not an accurate enough system of measurement. I think the next steps would be : 1. to add acid to the B solution so that both the CS and the B solutions are at the same level. 2. to use a 250ml container of CS and add a larger volume of B ( to reach the same ppm for each stage of the test ) and to decant from that to the test tube before adding the 2 drops of CU and taking the reading. Any other input would be appreciated.
 Admin P: 22,714 How concentrated is your hydrochloric acid? 30%? If so, you may assume your pH doesn't change with added drops of other solutions. Your diluted solution is around 3M, things you add are orders of magnitude less concentrated. I wonder how realistic it is to assume linear response from the sensor. After all, it is not following a single wavelength as it is should be done. Remember Lamber-Beer's law is linear only for a limited range of concentrations (but it shouldn't mean signal drifting back, it should mean signal saturation at some point). I don't think it should matter fro ppm levels, but who knows.
 P: 10 Hi Borek The carrier solution ( CS ) was made with 200ml distilled water and 100ml hydrochloric acid. The result was about pH 7.2 In the test tube it is then 13ml of the CS, and then 0.5ml ( or more ) of the Borate Solution ( pH around 8 ). I am not able to measure the pH of the combined solution in the test tube. I will do a test in the morning with a more acidic borate solution to see if the reagent causes any darker colors. sorry, forgot the details. Yes, it is 30% acid.