exchemist

If the product data does not mention approval for potable water applications, all that means is that it may not have been submitted for approval. It does not mean it is unsuitable, just that the relevant body may not have considered it for approval. The distinction between “suitable for” an application and “approved for” an application is one I remember well from my career in the lubricants industry. It can have implications for such legal things as warranties in some cases, but if that is not at issue it may not matter. From what your respondents can see from the MSDS, and from what we know of the chemistry and your intended application, we can see no appreciable risk.

A quick web search reveals there is a UK body called WRAS: https://www.wrasapprovals.co.uk that actually approves materials for use in potable water applications. They appear to have approved one or more silicone greases. If you are not in the UK, I have no doubt there will be equivalent bodies in your country.

A property, of a physical system of some kind, where the "physical system" may involve matter and/or fields (EM radiation consists of oscillating fields). (In English it is spelt "physics" by the way.)

It sounds as if this person has fallen into the old trap of the "Star Trek Fallacy", of thinking energy is a substance: some kind of "stuff". It isn't. Energy is merely a property of a physical system of some kind. So it's meaningless to say the photon is a flow of energy, unless he can say the energy of what, and what kind of energy it is. So I'm afraid it looks like run-of-the-mill crank physics, from someone who does not know much physical science, and thus not worthwhile for me to watch the video.

Yes I'm sure it will be fine. It is biologically pretty inert, as the MSDS shows, and if it's only on the O rings the quantity will be minute. Also it's not water soluble so should not come off into the water in any case.

Thanks for this. It makes sense. But how does CuSO4 catalyse this process?

Yeah, renormalisation. 👍 Cool.

Tell us about it and we can comment. (It's a rule of the forum that topics should not require participants to go off-site to another web address in order to find out what the topic is about.) Since physics has a satisfactory model of the photon already, perhaps the quickest way to elicit interest would be for you to describe what advantages this model has compared to the established one.

It's illustrating what can be made from what. A common game to test organic chemistry knowledge is to ask the student to show a route for synthesising a given compound, using only alkanes or something very simple as the starting point. We got very good at that in my first year at university. I still have a copy of R O C Norman's "Principles of Organic Synthesis" on my shelf. One learns a "vocabulary" of synthetic reactions, which can then be deployed to construct a wide range of molecules. This scheme shows you a range of steps that interconvert various types of organic functionality.

Then look them up on the internet. Type in each one and see what you get. I think you will get an informative answer for most if not all of them. From the sound of it, you may need to look also at the IUPAC system of nomenclature. Here is one teaching link for students on the topic: https://chem.libretexts.org/Courses/Sacramento_City_College/SCC%3A_Chem_420_-_Organic_Chemistry_I/Text/03%3A_Functional_Groups_and_Nomenclature/3.02%3A_Overview_of_the_IUPAC_Naming_Strategy As a general comment, I think these LibreTexts are not bad. You can learn (or in my case revise, as it is almost 50 years since I sat my chemistry Finals) quite easily from these I think.

Item 4 has no physical meaning. A solid cannot boil. Boiling is the development of bubbles in a liquid when the vapour pressure equals the pressure above the liquid. So you only need words for items 1-3, which we have.

Opening a book, or at least looking up pages on the web, rather than wasting time on videos, would be a good start. Videos are a terrible way to try to learn almost anything and this certainly applies to organic chemistry. To start with, have you found the chemical formulae for these organic compounds?

Indeed. In fact the thermoelectric devicesI was talking about are only ~10% efficient at best, I think. But that doesn't matter to a camper. You have plenty of heat available and what doesn't get turned into electricity performs a useful function of providing the heat of the campfire.

Probably not. You need a heat pipe to get heat out of the fire, the engine and generator and a condenser/radiator. I have seen pictures of a Stirling cycle engine used for this, but it was not very lightweight or compact. If you just want to run low power electronics and an LED light or two, and light weight is a priority, I would think a thermocouple (thermoelectric generator) might be a better bet. I've had a quick look on the web and it appears such devices are in fact commercially available.

I'm intrigued to see that the "thorn", present in Old English, is something used in Icelandic. The other characters I don't recognise. However I must agree with Markus that if you are interesting in discussing science, as opposed to striking an affected linguistic pose, you are better off sticking to the English alphabet. I've just tried to read your post and gave up in annoyance after only a paragraph.

Ssh, don’t tell Lara Knowles.

Good point, and yes, we had that discussion with that person who had a bee in his or her bonnet about microwaving silica gel, some months ago.

Why do you think mineral crystals are fractal in nature?

OK, yes I know that fractals exhibit the same patterns at different scales. But how is that applicable to systems as different as a mineral crystal and a living organism?

Your statement seems to be meaningless. To start with, what is this "complexity definition of invariance of scale"? Where can we find it? Can you recite what it is? Next, having established that, if we can, you need to explain what you mean by patterning, diversity and complexity being related due to this.

OK. Where would scale come into this? Or is this about “scale” , i.e the degree, of complexity?

What “phenomenon” are you talking about, and in what way do you think invariance of scale applies to it?

According to my recollection from the lubricants industry this phenomenon applies to sliding surfaces, rather than just a static contact. It leads to what is known as adhesive wear (as opposed to abrasive or corrosive wear). With sliding surfaces, microscopic asperities come into contact, causing very high pressures and temperatures at the contact zone which leads to microscopic welding of the surfaces at these points. As the sliding continues, these microscopically welded areas are torn asunder. Often this does not occur at the point where the weld formed, so that material is torn out of one or both surfaces. It is often the practice to use dissimilar metals in bearings, chosen so that the welds are weaker than the parent metals. This encourages the adhesions to break without tearing lumps out and thus preserving the surface. (One example is in worm gears, where the worm is usually steel and the gear wheel is bronze. Worm gears have an extremely high rate of sliding relative to rotation, so the issue can be quite acute in such gears.) The purpose of lubricants of course is to keep the surfaces apart and prevent this from happening. It is common practice to add anti-wear or extreme pressure agents - often sulphur/phosphorus containing organic molecules - to lubricants where the nature of the motion does not ensure a constant pressurised film of lubricant to do this, another classic example being the cam followers in an engine. The anti-wear agents decompose under local temperature, adsorb on the surface and form a protective but weak layer, that easily breaks without damaging the parent surface. However one does also get "cold welding" of clean flat metal surfaces brought into static contact. This occurs especially with surfaces exposed under vacuum, so that no oxide layer has a chance to form: https://en.wikipedia.org/wiki/Cold_welding.

Not if all our grandparents had it, surely?

All the features you list are common to a vast range of creatures, so would not be part of this 1-4% you are enquiring about. So we share DNA all of these, even though we are not directly descended from any of them. It is often said we share 50% of our DNA with a banana, even. But my understanding is the 1-4% relates to DNA features found in homo sapiens neanderthalensis but NOT found in homo sapiens sapiens of African origin. As for where it comes from, one needs to keep in mind that H sapiens sapiens and H sapiens neanderthalensis appear to have interbred. So they are not fully separate species. Therefore, if, like me, you are of N European ancestry, it is likely you have some ancestors who were Neanderthals, rather in the way that I have one Welsh great-grandmother.