What kind of hot plate/stove with stirrer to buy?

[Maget]

Hello
I m looking to buy a hot plate stove with stirrer but not sure what is needed.
What is max temp needed to work with chemicals?
I look for something cheap up to 65$ on ebay or aliexpress.
There is one cheap but it have 100/120V need EU with 220V.

 

[Lightspeed]

I would just buy a cheaper stove top, you know those portable ones, I just bought a single element one, plenty of other guys use them, kadriver, Palladium etc don't get anything flashy, in one year they look like a dogs breakfast anyway as we are dealing with corrosive concentrates.
Just get a separate stirrer if you must have one.
Temp wise I guess you need to get close to a boil depending on the liquid you are digesting with. Not sure of my logic but I have not needed a stirrer yet, I would prefer to stay present with my solutions, instead of being tempted to leave it unwatched on a heater/stirrer.

Most of the cheaper Chinese stuff is rated only to 220v, try to find one that has a rating up to 240v, it should last you longer, electrical component wise. I would not be tempted to run a voltage converter for a different countries power source voltage, either up or down respectively.

Not sure on what a reasonable budget is for a stirrer, depends on what you are digesting I guess. I would not be inclined to get too invested as I view both as having a limited lifespan with the corrosives we are using at heated temps, especially nowadays where good quality can cost a bit, maybe an old school solid state type stirrer from a Craigslist type of thing or Quokka platform.

 

[Maget]

I would just buy a cheaper stove top, you know those portable ones, I just bought a single element one, plenty of other guys use them, kadriver, Palladium etc don't get anything flashy, in one year they look like a dogs breakfast anyway as we are dealing with corrosive concentrates.
Just get a separate stirrer if you must have one.
Temp wise I guess you need to get close to a boil depending on the liquid you are digesting with. Not sure of my logic but I have not needed a stirrer yet, I would prefer to stay present with my solutions, instead of being tempted to leave it unwatched on a heater/stirrer.

Most of the cheaper Chinese stuff is rated only to 220v, try to find one that has a rating up to 240v, it should last you longer, electrical component wise. I would not be tempted to run a voltage converter for a different countries power source voltage, either up or down respectively.

Not sure on what a reasonable budget is for a stirrer, depends on what you are digesting I guess. I would not be inclined to get too invested as I view both as having a limited lifespan with the corrosives we are using at heated temps, especially nowadays where good quality can cost a bit, maybe an old school solid state type stirrer from a Craigslist type of thing or Quokka platform.

Your help is appreciated.
I also was thinking to buy that type stove top but wanted 2 in 1 with stirrer.
Have talked with my friend he say that we could convert that one to 220V supply, so i m still looking.
Between this is the one with 100v/120v US voltage that I look to buy and convert, it will cost 66.72$ total with shipment, which is affordable. I even asked the seller if he can show the insides to see what's there, but not sure if he will do that.
Thank you.

 

[Lightspeed]

No problem @Maget, keep in mind your glassware when looking, sometimes it's easy to overlook the size of the pan surface area on stirrers/heaters.

I only use low form beakers and mainly 5000ml nowadays, low form as the surface area is much greater and aids in managing containment of mistake reaction acceleration boilovers, also allows for more surface area contact when heating. Currently I am mostly working on silver refining, so large solutions are normal for me. When I do gold I usually only run inquartation in prep for turnover to refinery because i want to extract the silver from karat alloys anyway unless I want to go all the way to bullion, currently at the Perth Mint Refinery, it does not matter what grade metal you turn in, they will charge you for refining, if you want to have a parcel processed, they charge per metal recovered, so it makes no sense for me to turn in karat alloys because the fee is double.
I even turned in assayed by icp silver crystal with icp results at 9995 minimum, 220 ounces troy, they still charged me for refining, this is why I do not really need a stirrer facility.
I may work on AR again in the future so it really depends on your personal target metals to refine and chosen processes and how you will sell your finished product.

The worst I have dealt with is the exothermic reaction by running conversion of Silver Chloride, but heat is not needed anyway, thus low form beakers to handle the reaction potential of overflow.

Cost wise if its affordable and you want to give it a crack and it makes logical sense to you for your intentions, then go for it.

If you are heating your solutions, remember to use a safety net by placing your beaker in a larger vessel in the case you do have run away reaction so you will not lose your metal, I just use corningware pyroceramic, it cleans easily and will put up with alot, I have never lost a piece yet from heat expansion. The downside is you are losing alot of direct heat through its insulating effect, but that is something that does not bother me, its just not worth it to lose you metal from an unforseen run away.

I think my little single element portable stove cost me around $36 Aud, so they are pretty inexpensive made from now rusty cheap stainless grade.

If you have a friend that can help you with the electronic side of things for your mains voltage, that will be handy for you.

All the best mate whatever you decide, don't forget to post your first recovery and refined product.

Kind Regards
Benjamin.

 

[Maget]

Hi
I plan to recover silver, gold, platinum, palladium, rhodium and other precious metals.
Still would like to know maximum temp I will need to achieve.
Maybe someone can suggest.
Thank you for all the help so far.

 

[Lightspeed]

As I said you will need to heat to a boiling point, this so to accelerate reactions, ut boil to help neutralise acids in solution like preparing electrolytes or pre copper cementing, so heating to around 100c is necessary but depends on the acid and water ratio, but 100c should be sufficient as its water boil temp, anything over is good so you can dial it down without running your heater electrics at maximum

 

[Maget]

As I said you will need to heat to a boiling point, this so to accelerate reactions, ut boil to help neutralise acids in solution like preparing electrolytes or pre copper cementing, so heating to around 100c is necessary but depends on the acid and water ratio, but 100c should be sufficient as its water boil temp, anything over is good so you can dial it down without running your heater electrics at maximum

This clears up everything, thank you.

 

[Jimbriese]

If you cannot find something setup for 220v EU you can find a cheap transformer 220 primary and 120 secondary. Wire the primary with a cord and an outlet to the secondary. This will work with a hot plate stirrers non digital and the frequency will not make much difference in the application. Just be careful when doing this as US uses 60hz and EU is 50hz and some electronics will not work.
Now I’m not 100% on EU but to get the 120 in US is one hot leg to ground to see if it works there take your meter and stick one probe in the ground and the other into one side of an outlet and see if it reads 110-120 if so. you can get a ground rod copper or galvanized about 1/2in diameter and about six foot long drive into the ground leaving just enough to connect to sticking out of the ground and connect from one leg to an outlet US and then run from the outlet to the ground rod to get the 120v outlet to run the hot plate on.

 

[eaglekeeper]

I also use those cheap single coil stove top broilers and a separate stirrer that I rarely use. You should consider those broilers as a consumable because Hcl eats them up over time. If you decide to buy a hotplate/stirrer there's a couple things to consider. As Lightspeed said, the surface area should accommodate the size of your beakers. It should also accommodate the weight of your solutions. The plate should be ceramic coated, Hcl will destroy unprotected stainless steel. Keep it away from acid fumes as much as possible when not in use.

As for the stirrer function.... they are only strong enough to stir solutions with some lite to medium solids.

 

[Jimbriese]

I have a cheap electric hot plate I use for warming solutions. I have a Coleman butane campstove ($20 at Walmart and $3 for a can of fuel) which is short and compact enough to use For distillation I find the visible flame easier to adjust temps and the cheap hot plate barely get hot enough to boil water in a pan with direct contact but it works great for the small batches I run.

 

[4metals]

I've only used single or double pancake griddles for the last 20 years and when necessary an overhead mounted stirrer. The size of the griddle accommodates the largest beakers, and as has been said, you need to be sure the entire beaker fits on the heated surface or the thermal difference will break the glass. As far as an overhead stirrer, in this era of cordless drills, most of us have an old chuck drill which is likely variable speed which makes a great drive motor for a coated propeller and shaft. Much more powerful than a spin bar.

If I could only recoup the insane cost of "laboratory" stir / hot plates I've spent over the years I could take a wonderful vacation.

 

[Shark]

I like the griddles as well. My reasoning maybe a bit different than 4metals though. I can run multiple solutions on the larger griddles. This can be a big plus if you need to reduce more than solution. I still keep a single hot plate handy and use it when I am working on a single solution or need to rush a smaller batch.

 

[orvi]

I personally use cheap electric hotplate (5 L beaker is also OK with it) and lab magnetic stirrers with heating element. Ability to stirr the mixture is very good advantage, for example if you are preparing silver oxide from silver chloride in less than 200-400g quantity. There are suitable stirbars for this, motor and magnet have enough power to keep it fluid... And you can do other stuff, while it is happily converting at temperature you set in.

Overhead stirrer is very practical thing and also suited for bigger aplications, but it need steady RPM management. Drills are conveniently designed to regulate power to the motor, not always RPM. There can be situations, when you start with thick paste hard to stirr, so you adjust the "power" for good stirring, but over time, solution gets more runny and motor start to speed up and splashing the stuff around or worse. With good regulator, no problem here, but you need to be cautious.

 

[eaglekeeper]

Overhead stirrer is very practical thing and also suited for bigger aplications, but it need steady RPM management. Drills are conveniently designed to regulate power to the motor, not always RPM. There can be situations, when you start with thick paste hard to stirr, so you adjust the "power" for good stirring, but over time, solution gets more runny and motor start to speed up and splashing the stuff around or worse. With good regulator, no problem here, but you need to be cautious.

Would a drill with a brushless motor solve your RPM problem?.. I believe they have a speed sensor circuit to control the motor..... I don't know brushless that well, just a thought.

 

[PeterM]

Based on my experience running AR 24/7 on ores and never wanting a breakdown, I found the CAFRAMO mfg in Canada make that best bang for the buck $$$ that lasts and lasts. Check eBay and you'll find one. I used a Teflon coated stirrer. I have gone through a dozen Thermoline stirrers and Caframo is the REAL DEAL. Hot plates are cheap everywhere so are timers. If buying it used, it must have the chuck key because it's a special key unlike anyone elses. Be sure to buy a good Lab Stand to support it. To me, do it right from the beginning don't buy crap and think your going to get the job done.
P

 

[Geo]

When shopping for a hot plate stirrer, be sure to note the capacity. If it is a 1L capacity, trying to stir 2L will burn out the stirrer quickly. Older hot plate stirrers are analog and are much more hardier than the newer, cheaper, solid state models. Where an analog model can be repaired if need be, solid state models are usually trash if something on the board burns out. Remember, you get what you pay for.

 

[Geo]

I bought a cheap cordless drill so that I could use stir rods. I also bought a couple of stir bar retrievers to sacrifice for the PTFE coated rods as extension rods. I drilled holes in my hoods on the top to pass the rods through. I attach the rod to the drill and the drill sits on a wooden support I built for it. I basically built an overhead stirrer.

 

[orvi]

You can test it easily. Set some "power" or "RPM" on the drill and stick it to the thick suspension of something (anything like AgCl, mud, clay, gelatin, glycerin etc... anything just hard to stirr). Then add water to thin the suspension/solution/emulsion and carefully watch the RPM. If it start to go faster and faster, it does not have RPM control, but just power control, regardless of RPM.

I repeat that this is only an issue if you are dealing with suspensions or thick stuff, which could eventually thin out and cause this problem.

I mention one of my experiences, when this almost caused a disaster. We processed a large batch of PGM powders, it was like more than one kilorgam. Added AR, reaction started, we adjusted drill stirrer (with just power regulation, not RPM - we didn´t realized the issue to the point). It started to stirr nicely, swirling the heavy powders nicely from the bottom. I left to take the lunch, but the time when I returned, I heard a very concerning splashy/rattling noise from the lab. I rushed in and saw the drill going very fast inside, causing the whole 5 L beaker to rattle and dance a bit on the hotplate, with bits of suspension splashing around to the catchpan.
Issue was, that we set (and I say again, we do not realized this issue till it happened) the drill to some POWER, not RPM. And as some PGMs passed to the solution, there were less and less of heavy precipitate, so there was not nearly as much to move around, so the drill started to turn like crazy, because nothing was slowing it down
I couldn´t blame the regulator circuit, it just done what it should done - regulate POWER. Classic drill regulators are either triac or PWM - and these are power regulators. That is why I like magnetic stirring plates, because you set the RPM and it will hold the speed.

 

[Geo]

You can test it easily. Set some "power" or "RPM" on the drill and stick it to the thick suspension of something (anything like AgCl, mud, clay, gelatin, glycerin etc... anything just hard to stirr). Then add water to thin the suspension/solution/emulsion and carefully watch the RPM. If it start to go faster and faster, it does not have RPM control, but just power control, regardless of RPM.

I repeat that this is only an issue if you are dealing with suspensions or thick stuff, which could eventually thin out and cause this problem.

I mention one of my experiences, when this almost caused a disaster. We processed a large batch of PGM powders, it was like more than one kilorgam. Added AR, reaction started, we adjusted drill stirrer (with just power regulation, not RPM - we didn´t realized the issue to the point). It started to stirr nicely, swirling the heavy powders nicely from the bottom. I left to take the lunch, but the time when I returned, I heard a very concerning splashy/rattling noise from the lab. I rushed in and saw the drill going very fast inside, causing the whole 5 L beaker to rattle and dance a bit on the hotplate, with bits of suspension splashing around to the catchpan.
Issue was, that we set (and I say again, we do not realized this issue till it happened) the drill to some POWER, not RPM. And as some PGMs passed to the solution, there were less and less of heavy precipitate, so there was not nearly as much to move around, so the drill started to turn like crazy, because nothing was slowing it down
I couldn´t blame the regulator circuit, it just done what it should done - regulate POWER. Classic drill regulators are either triac or PWM - and these are power regulators. That is why I like magnetic stirring plates, because you set the RPM and it will hold the speed.

Most drills today have "variable speed control". The speed is set by the trigger/switch and not the current load. It's the same as a sliding rheostat. Regardless of load, the speed should stay the same.

 

[orvi]

Most drills today have "variable speed control". The speed is set by the trigger/switch and not the current load. It's the same as a sliding rheostat. Regardless of load, the speed should stay the same.

That is the good stuff. Unfortunately, still a lot of cheap stuff have only triac regulator, which is OK for the grinder or basic simple drill... But for this application, variable speed controller is much better, as you say.