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Lowest Possible Usage Temperature Of Petrol?
I read somewhere the other day, that the lowest temperature diesel can be used is approx -23 degrees centigrade. Below this temp it turns to 'gel'. What is the temperature at which petrol does this, if it does?
cheers
alec
cheers
alec
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To begin with, you have to appreciate that petrol is not a single chemical. It is a concotion of various hydrocarbons. Some of these hydrocarbons are fairly viscous whilst others are thinner than water. Petrol also contains aromatics which are normally gaseous at room temperature. By their nature, the viscous hydrocarbons will solidify before the aromatic hydrocarbons
Petrol has what is known as a "flash-point" of around -71.7 degrees Centigrade, give or take a few degrees depending on the exact composition of the petrol. At this temperature, petrol is still a liquid and this flash-point is the temperature at which the vapour of petrol will catch alight. Now, as you can imagine -71.7 degrees Centigrade is a very low temperature - but it gets worse.
The more viscous hydrocarbons contained within petrol will become solid within a wide range of atmospheric temperatures. However, the aromatic hydrocarbons will not solidify until around -129 degrees Centigrade to around -185 degrees Centigrade - the composition of the petrol again plays a part in this.
Sometimes miniscule amounts of water are present in petrol. This water will freeze-out at the same temperature as it does in the environment ie 0 degrees Fahrenheit.
So, to answer your question petrol, unlike diesel, does not become a gel.
To summarise, if you asked what was the freezing point of petrol I would have said anything between -71.7 degrees Centigrade and -185 degrees Centigrade.
Apologies for the lecture!
Petrol has what is known as a "flash-point" of around -71.7 degrees Centigrade, give or take a few degrees depending on the exact composition of the petrol. At this temperature, petrol is still a liquid and this flash-point is the temperature at which the vapour of petrol will catch alight. Now, as you can imagine -71.7 degrees Centigrade is a very low temperature - but it gets worse.
The more viscous hydrocarbons contained within petrol will become solid within a wide range of atmospheric temperatures. However, the aromatic hydrocarbons will not solidify until around -129 degrees Centigrade to around -185 degrees Centigrade - the composition of the petrol again plays a part in this.
Sometimes miniscule amounts of water are present in petrol. This water will freeze-out at the same temperature as it does in the environment ie 0 degrees Fahrenheit.
So, to answer your question petrol, unlike diesel, does not become a gel.
To summarise, if you asked what was the freezing point of petrol I would have said anything between -71.7 degrees Centigrade and -185 degrees Centigrade.
Apologies for the lecture!
No apologies are called for Gef - I clearly need to explain further.
I stated that: " Petrol also contains aromatics which are normally gaseous at room temperature".
When I referred to "aromatics", I was not referring to aromatic hydrocarbons, which is what you, as a chemist, appear to have assumed.
I was referring to the volatile organic compounds some of which are impurities in petrol, whilst others are deliberate additives. These impurities and additives, readily enter the gaseous phase - you will note that at no point did I state that these aromatics were a "gas" in their original form or were a "gas" at room temperature - I said they were "gaseous".
The principle definition of "aromatic" in the OED is:
"Having the fragrant smell, and warm, slightly pungent, taste, of spice; yielding aroma; spicy, fragrant, sweet-smelling"
Do you not consider that this definition applies to petrol?
Furthermore, historically following the work of Faraday et al in 1825 and subsequently with an oily substance in the base of coal-gas storage tanks, what we know now as "aromatic hydrocarbons" were named thus precisely because they were fragrant. Harmful that they are, you surely concede that benzene, toluene, xylene and others in the series have a pleasant, fragrant odour.
Continued:
I stated that: " Petrol also contains aromatics which are normally gaseous at room temperature".
When I referred to "aromatics", I was not referring to aromatic hydrocarbons, which is what you, as a chemist, appear to have assumed.
I was referring to the volatile organic compounds some of which are impurities in petrol, whilst others are deliberate additives. These impurities and additives, readily enter the gaseous phase - you will note that at no point did I state that these aromatics were a "gas" in their original form or were a "gas" at room temperature - I said they were "gaseous".
The principle definition of "aromatic" in the OED is:
"Having the fragrant smell, and warm, slightly pungent, taste, of spice; yielding aroma; spicy, fragrant, sweet-smelling"
Do you not consider that this definition applies to petrol?
Furthermore, historically following the work of Faraday et al in 1825 and subsequently with an oily substance in the base of coal-gas storage tanks, what we know now as "aromatic hydrocarbons" were named thus precisely because they were fragrant. Harmful that they are, you surely concede that benzene, toluene, xylene and others in the series have a pleasant, fragrant odour.
Continued:
The Academic Press Dictionary of Science and Technology defines gaseous as:
"Physics: Existing in the state of a gas as opposed to liquid or solid state".
The OED more interestingly defines gaseous as:
"Having the nature or in the condition of gas" and refers to a "vaporous or gaseous state"
It would seem from these definitions that it is perfectly correct to attribute the fragrant vapour that emanates from petrol in this manner. Despite failing sometimes, I do try to be as non-technical as possible on AB - we are not after all on Google Usenet forums.
Incidentally, whilst I agree that there are no aromatic hydrocarbons that are a gas at room temperature, there are a considerable amount of volatile, organic compounds with aromatic properties that are - look them up in Beilstein. Some of these compounds are present in petrol.
It never ceases to surprise me how a word such as aromatic can mean different things to a chemist and a layman.
"Physics: Existing in the state of a gas as opposed to liquid or solid state".
The OED more interestingly defines gaseous as:
"Having the nature or in the condition of gas" and refers to a "vaporous or gaseous state"
It would seem from these definitions that it is perfectly correct to attribute the fragrant vapour that emanates from petrol in this manner. Despite failing sometimes, I do try to be as non-technical as possible on AB - we are not after all on Google Usenet forums.
Incidentally, whilst I agree that there are no aromatic hydrocarbons that are a gas at room temperature, there are a considerable amount of volatile, organic compounds with aromatic properties that are - look them up in Beilstein. Some of these compounds are present in petrol.
It never ceases to surprise me how a word such as aromatic can mean different things to a chemist and a layman.
Point taken prof. Also I should point out that although no aromatic (in the chemical sense) compound is a gas at room temperature many of them are very volatile and so evaporate easily at room temperature. This is why we can smell them. And yes, they do smell nice. My favourite is nitrobenzene; very similar to marzipan.
Perhaps I have inhaled to many of them during my career :-)
Perhaps I have inhaled to many of them during my career :-)
Many thanks Gef. You are absolutely right to highlight the volatile nature of some aromatic hydrocarbons.
I've never been that fond of nitrobenzene because of that almond-like marzipan smell - I can't stand the taste or smell of marzipan and I take it off the cakes the wife brings home.
While I've always been fond of the smell of some of the Cellosolve variants, my own personal favourite amongst the arenes has always been toluene. Wherever possible, whenever something needs reparing at home, I let the wife use the Evo-stick. I am all too well aware of the risks of permanent brain damage with toluene but........sorry, I forgot what I was about to say.
Oh well, time to scratch the ulcers inside my nose again!
I've never been that fond of nitrobenzene because of that almond-like marzipan smell - I can't stand the taste or smell of marzipan and I take it off the cakes the wife brings home.
While I've always been fond of the smell of some of the Cellosolve variants, my own personal favourite amongst the arenes has always been toluene. Wherever possible, whenever something needs reparing at home, I let the wife use the Evo-stick. I am all too well aware of the risks of permanent brain damage with toluene but........sorry, I forgot what I was about to say.
Oh well, time to scratch the ulcers inside my nose again!
4lec:
You are absolutely correct with your proposition that petrol can be used at lower temperatures than diesel in very cold conditions as diesel does indeed gel.
I know next to nothing about motor vehicle technology, so I'm not in a position to give you an opinion of the usage of petrol over diesel in Russia. I can give you some pointers that may be useful all the same.
I went out Moscow and some other former USSR cities a few years back and I've also been on holiday on Finland - part of it north of the Arctic Circle.
What we now call Russia is surprisingly temperate and often has a temperature range similar to our own in the UK, sometimes even in winter. This is because a whole swathe of Russia is at approximately the same latitude as the UK. The closer you get to the Arctic Circle, the colder it becomes and the temperature in Siberia etc is absolutely perishing at its worse.
Likewise, Finland is approximately as temperate as the UK around Helsinki, but when you reach Lapland its a different story - the vehicles I rode in around Lapland were petrol only and I cannot recollect seeing any diesel.
I'll take an educated guess on this basis and say that the diesel is probably ok in the southern latitudes in Russia, but petrol would be increasingly called for at higher latitudes.
I also read a few weeks ago that diesel is often of poor qulity in Russia and can contain serious impurities and adulterants. It was because of this that BMW delayed introducing one of their latest vehicles to the country until they cleaned up their act.
There are also mixtures of ethanol with petrol and methanol with petrol. These hybrid fuels have different properties to pure petrol alone in many respects.
You are absolutely correct with your proposition that petrol can be used at lower temperatures than diesel in very cold conditions as diesel does indeed gel.
I know next to nothing about motor vehicle technology, so I'm not in a position to give you an opinion of the usage of petrol over diesel in Russia. I can give you some pointers that may be useful all the same.
I went out Moscow and some other former USSR cities a few years back and I've also been on holiday on Finland - part of it north of the Arctic Circle.
What we now call Russia is surprisingly temperate and often has a temperature range similar to our own in the UK, sometimes even in winter. This is because a whole swathe of Russia is at approximately the same latitude as the UK. The closer you get to the Arctic Circle, the colder it becomes and the temperature in Siberia etc is absolutely perishing at its worse.
Likewise, Finland is approximately as temperate as the UK around Helsinki, but when you reach Lapland its a different story - the vehicles I rode in around Lapland were petrol only and I cannot recollect seeing any diesel.
I'll take an educated guess on this basis and say that the diesel is probably ok in the southern latitudes in Russia, but petrol would be increasingly called for at higher latitudes.
I also read a few weeks ago that diesel is often of poor qulity in Russia and can contain serious impurities and adulterants. It was because of this that BMW delayed introducing one of their latest vehicles to the country until they cleaned up their act.
There are also mixtures of ethanol with petrol and methanol with petrol. These hybrid fuels have different properties to pure petrol alone in many respects.
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