I'm interested in learning what substances (either liquid or solid)
will cause notable changes in the color of water but not of diesel
fuel.  The chemical/substance should be "safe" in the sense that it
does not require special treatment other than perhaps wearing a pair
of nitrile or latex gloves.

This is all so that I can take a small amount of this with me when I
buy diesel fuel for bluewater sailing -- water in diesel is a BIG
problem if you discover it when 1000 miles offshore!

Since diesel is often dyed for tax identification purposes, I need
something that those diesel dyes will not effect or be confused with.

I want something that I can add to a small (10-25ml) sample of the
potential fuel before purchase.  If the substance "detects" (reacts
with?) a meaningful amount of water and then causes a visible change
in color then I won't fill up there.

So in recap, what types of substances will:

1) Change the color of water dramatically and visibly,
2) Not change the color of the diesel fuel itself in the absence of water
3) Be a quick reaction, (faster than just waiting for the water to
separate which is what we do now...hours, ugggh)
4) Be a safe reaction,
5) Not require large amounts and be easy to carry.

What do the members of the oracle suggest?

Why don't you just use a filter.

http://www.dieselproducts.com/dahl/dahl.html

http://www.allsyntheticsgroup.com/dahl.html

I do filters; both as part of the fillup and two Racor filters in-line
in the fuel system.  They work reasonably well for the most part,
but...  I'm haunted by the story of a friend who, on a very very big
boat, went through 150 Racor filters in a week because they had taken
on a large amount of very very watered fuel in Fiji.  The fact that he
had 150 filters to use was what saved his employement - he had thought
ahead for a transpacific sail.  I don't want to rely soley on filters
if I can avoid the problem in the first place.

This is a real amateur comment, but in Scandinavia in winter, they put
a little alcohol in the Gas/benzin tank, which mixes with the water
from condensation, and avoids a "water lock" at the base of the gas
tank. I assume the alcohol-water mix is then lighter that the gas or
mixes with it.
Would this avoid or minimize your problem?
What about a simple centrifuge to speed the separation of water and
oil?  Just a little thing that would spin your 25ml (shot glass sized)
sample horizontally and let the container sink back to the vertical
slowly when turned off so that the liquids remain separate, maybe with
a container that has an slight "bottle-neck" at the critical level
that would help avoid the oil and water mixing again???
Should I apply for a patent?  :)

Robust, battery-powered, pocket-sized centrifuges do exist - they are
commonly used by veterinarians who wish to centrifuge blood samples
(microhematocrit tubes) while in the field.  Blood is sucked into a
capillary tube which in turn is plugged with putty.  The tube is spun
in the small centrifuge for a few minutes, and the hematocrit value
(the fraction of blood volume consisting of red blood cells) can be
read off using a special ruler.

This might work with diesel samlples, but I guess the centrifuge will
be quite expensive (a few hundred US$)...

If a centrifuge could do the job, I imagine that something cheaper
than a medical one could be deviced to do the job.
It now occurs to me that in a stationary tank of diesel fuel, the
water would accumulate at the bottom, probably near the pump's pipe or
at drain, if the oil is taken out by gravity.  This could confuse the
matter, no matter how you tested; drawing off a little to test would
just give you what was in the end of the hose, which - if the noozle
had been hung up and there hadn't been much activity - could contain
less water than what you got from the bottom of the tank.

Centrifuges are nice....but:

1) Are likely to be more expensive than I want (at the start, for the
1000th use that may not be true)

2) A tad bulky, a problem in an environment where space is at a premium

3) Slow - they stil rely on separation

4) Difficult to use accurately - it does not take much water to cause
a problem.  To be able to see a small amout of water in the bottom of
a test tub will be difficult.

No, I really want a colormetric test and reagent. 

Thanks for the help sp far though.



VJ

My worries are primarily related to when I buy fuel outside the US. 
For instance, there are a number of places on the Baja Penisula in
Mexico that are reprted to have dicey diesel.

VJ

How about testing with a small dessicant-crystal? You can try with one
that liquiefies if water is present (like calcium chloride etc.) or
one that changes color (like silica gel with added cobalt chloride or
perhaps simply pure anhydrous cobalt chloride crystals)?

You might need to experiment a bit to figure out the best size of the
crystal, and to make sure the test isn't too sensitive; but the
equipment (test tube ? chemical) is cheap and the chemicals are safe
to use.

:-) Re

That's EXACTLY the type of thing I'm interested in.  But I'm not a
chemist.  Can you expand on your ideas and list?

Thanks,

Jim

Jim,

If you pour a small amount of diesel in a glass that contains silica
gel or dried calcium sulfate that has been colored with cobalt
chloride, the cobalt chloride will turn from blue, when dry, to pink
upon contact with any water ? whether the water is emulsified (with
alcohol or whatever) or not.  Sounds good but won?t work for your
purpose.  As you may know, diesel most always contains a very small
amount of water (condensation in holding tank, etc.) and will turn the
cobalt chloride pink in no time upon exposure to most any diesel from
a commercial pump.  In fact, a short exposure of a desiccant colored
with cobalt chloride to open air on a dry day will turn it pink from
the moisture in the air ? much too sensitive.

The aforementioned idea of mixing in alcohol will emulsify small
amounts of water, as will many commercial diesel additives that
contain emulsifiers.  There are two problems with this:  Water, finely
divided and mixed with the diesel, is still water and will not only
rust the injector pump but, more importantly, when it reaches the
injector nozzles it turns into steam and in time blows out the
injector tips.  Other additives contain demulsifiers that work to
break up and drop the water molecules out of the fuel suspension at
the point of the holding tank and in the water separator (at filter)
so that it collects in the water bowl and does not travel through the
FIE components.  Demulsifiers act to keep most of the water at the
bottom of the fuel tank.  Of course if you get a load of diesel
heavily laden with water nothing is going to help short of mechanical
removal.  As you stated, contaminated fuel needs to be detected before
it goes in the tank.

During the preflight inspection of planes, a small amount of fuel is
drained from the bottom of each tank into a small clear cup or tube
and visually examined for a meniscus, indicating a boundary layer
between any water and fuel.  If water is detected, the tank is drained
little by little until the water layer (bottom) is gone.  A small
amount of a solution of cobalt chloride (obtainable from any chemical
supply house; check Internet) can be added drop wise to the sampling
cup to easily discern the water layer; it will turn the water bright
pink.  Surely there are many dyes that are soluble in water while
insoluble in oil (diesel) that can be used the same way.  The problem
here is that what first comes out of the vender?s pump may be quite
different, in regards to water contamination, than what comes out at
mid fill or later.  It wouldn?t be practical to do checks from the
filling nozzle every few minutes while taking on fuel.  Do your tanks
have accessible bottom drains?  If the bottom of the tank is
accessible, a flush mounted sampling drain (spring loaded), as used on
aircraft, could be installed.  They don?t corrode and very rarely
fail, as you might imagine, being approved by the FAA.  After taking
on fuel, a sample can be taken and, if found containing water, the
water can then be easily drained without loosing the fuel, the water
settling on the bottom of the tank.

I hope this helps.

I am working as the Technical Manager of a Petroleum Marketing Company
and am conversant with Diesel. All Diesels do contain water &
sediments to the extent of 500 ppm which will be very difficult to
eliminate. But if the presence is more than that, the best way is
elimination by opening the water drain of the fuel tank once in a day.
Water has a density of 1 whereas the density of Diesel is about 0.84.
In the storage tank, Water always settles below the oil and it is easy
to drain it. Once you see oil is coming out of the drain, stop
draining.

That does not solve the problem: you're removing water after it is in
the tank.  I want to minimize the amount of water I buy by not buying
diesel that is contains too much water....

vsssarma-ga,
Finally an expert!  How fast do water and diesel separate, say, after
refilling a stationary tank?
Condensation can't be much of a problem in Mexico, I expect, but even
that in a closed tank would be a quite limited source of water.
The story from Fiji may be true, but now it is beginning to sound more
like a case of intentional adulteration.
In a "civilized" place, it would seem that drawing off a 5 gallon tank
to start with would eliminate the problem.  One might even be able to
insist that seller take back the 5 gal.
Any ideas?
Myoarin

Diesel is stored in storage terminals in huge tanks which I am sure
many of you have seen. Diesel is pumped into these tanks taken either
from ships by pipeline transfer or through rail wagons or by road
tankers. Whatever the method, it takes typically 8 hours for the water
to settle down in the tank. After this period, just drain off the
water and use Diesel.