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Silica gel versus gasoline

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Willen

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I am talking about white (milky white) small silica gel balls normally we get a small packet with new device buying. As I hear a 100 miligrams ball can absorb 40mg moisture. 40% of its body. Acually what is moisture? Just related to 'water'? Does it absorb gasoline/diesel etc too?

When I put these milky white gel balls into water, these ball will be converted into transparent. So used to understand : milky white means gel is fine and transparent means the gel is expired or absorbed full moisture. Yesterday I had put such gel balls in gasoline but I got the balls more milky white than before. What that mean?
 

gophert

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First, dry silica gel granules have void spaces and those void spaces mean there is a change in refractive index as light passes through. The milky white means there is a lot of reflection and scattering of light. This makes sense as air has a refractive index of ~1 and silica is about 1.4

As it absorbs water, the void space fills with water and appears more clear. Water has refractive index of 1.33 so not perfectly clear but much clearer than dry silica.

Gasoline hates silica gel because the polarity is so different (Gasoline is essentially a low viscosity oil). Anyhow, dry gasoline can interact more with the last bits of water in the silica gel more than it does with the silica - the last bits of water in the little gel particles can be extracted by the gasoline. Even though gasoline can only dissolve 0.02% water (max), the huge amount of gasoline vs water can pull some water from the silica gel. In normal conditions, very dry silica gel will pull water from gasoline but, if you add already hydrated silica gel to dry gasoline, the gasoline can pull water from the silica gel and make the silica gel appear even more "milky".
 

gary350

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Are you trying to remove water from gasoline? If you read Chemical Formulary I think volume 9 you learn refineries formulate gasoline to contain up to 9% water in summer in hot weather geographical areas and less water in northern geographical locations. In winter cold weather gasoline contains only about 2% water and places like Alaska 0% water. When gas burns in an engine water turns to steam which is an increase of 1800 volumes of the water. This steam actually produces a bit more power than 100% gasoline. If you want to remove water and alcohol from gasoline pour 1 pint of water into 1 gallon of gas, alcohol mixes much better with water than gas so the 1 pint of water you add pulls all the water and alcohol from the gasoline. Now you can pour off 100% gas leaving water alcohol mix in the bottom of the container. Distill the alcohol water mix alcohol boils off at about 187 degrees F. I remove alcohol from gasoline for 2 reasons, 100% gas in the lawn mower will not destroy the carburetor then I can burn the distilled alcohol in my hobby jet engine.



 
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gophert

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I think volume 9 you learn refineries formulate gasoline to contain up to 9% water in summer in hot weather geographical areas and less water in northern geographical locations.
I'm not sure you've learned real chemistry from that volume. Gasoline cannot be formulated with 9% water any month of the year. Max possible content of water in non-oxygenated gasoline is 0.02% and about 0.5% for oxygenated fuel (i.e. gasoline with 10% ethanol).
 
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