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Hi all,
I am posting this for a colleague.  Since we have an active discussion 
on water testing, I thought this would be an appropriate time to post it.
Thanks,
Beryl

-------- Original Message --------
Subject: 	bottles
Date: 	Wed, 30 Jan 2008 09:08:02 -0500
From: 	Martha_BarrettSmith <[log in to unmask]>
To: 	[log in to unmask]



Hi Beryl,
Here is a brief and, I hope, complete description of our chemistry 
questions:

We are using 4 oz hi-density polyethylene translucent bottles for our 
water samples.  The "typhoid" samples contain a mixture of 50/50 vinegar 
and Lowell tap water, which is very slightly basic compared to distilled 
water.  For the "clean" samples, we are using Lowell tap water.

Question 1: We are considering switching to using distilled water in the 
"typhoid" samples, thinking the samples will retain their acidity longer 
than they would with Lowell water.  They might also come out brighter 
pink, which would be good.  Does this sound like it would work?

Question 2: Will the plastic of the bottles, over time, degrade the 
water itself in any way so that its pH will change and give us a bad 
reading (i.e., the red cabbage juice will not react and give us the 
correct color)?

Question 3:  Should we consider adding something slightly basic to the 
"clean" samples to help them maintain their alkalinity over time and if 
so, what is recommended that will a) be non-toxic, and b) not change the 
tension/viscosity of the "clean" samples (we tried clear Tilex, but it 
made the water pour out of the bottles uncontrollably)?

If you can get any info on this it would be great.  Thanks--
Martha



-- 
Beryl Rosenthal, Ph.D.
Director
Tsongas Industrial History Center
Boott Cotton Mills
115 John Street
Lowell, MA 01854
(978) 970-5081 (t)
(978) 970-5085 (f)
[log in to unmask]
www.uml.edu/tsongas

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