How to measure saturated salinity and mineral levels for flaked sea salt?

Question

I am a sea salt enthusiast looking to make the perfect flakey sea salt. I start with sea water and boil it down to a thick brine. Then with less heat I reduce the brine more slowly and inverted salt flake pyramids are made. I am looking for tools/instruments that will help me measure/understand the content of the brine (mineral content and salinity). Sometimes I get perfect flakey salt pyramids like the photo attached and sometimes I get I get more chunky results. The temperature of the brine is always the same but I get different results at times. This leads me to think that its the content of minerals in the saturated brine solution.

Are there chemistry tools/instruments I can use to understand the actual chemical/mineral makeup of the brine that is turning to salt.

Answer 1

Why not use salt (NaCl) bought from a store, or even better at a defined purity grade from a chemical vendor?

When you use sea salt, you get lots of other ions but more importantly you get colloidal particles, organic substances, and other compounds that will affect the crystallization. Chunky results sounds to me like a colloid particle that started crystallization in all directions at once.

If you want perfect crystals, do it perfectly, i.e. with a pure solution, in a clean and new glassware or polished stainless container. If you want perfect crystals you have to reduce the new-age-ness of it ;)

As for understanding, nobody fully understands crystallization, but a lot of things are known. There are books on this topic, check amazon and search for "crystallization". As for instruments, x-ray fluoroscopy and diffraction wouldn't be amiss but you will get very far with an optical microscope, I know I can watch crystals through a microscope for hours and still find something interesting. Barring XRF, XRD and microscope, and within a household budget there are salinity measurement probes and conductance measurement probes which will be able to tell you something of the brine such as it is.

Answer 2

What to measure??

Commercially available sea salts on the market today vary widely in their chemical composition. Although the principal component is sodium chloride, the remaining portion can range from less than 0.2 to 10% of other salts. These are mostly calcium, potassium, and magnesium salts of chloride and sulfate with substantially lesser amounts of many trace elements found in natural seawater. Though the composition of commercially available salt may vary, the ionic composition of natural saltwater is relatively constant. https://en.wikipedia.org/wiki/Sea_salt

The conclusion from Wikipedia seems to be that the composition of natural seawater is relatively constant (but complex!), while the dry commercial sea salt is quite variable, probably due to differences in production. Commercial table salt is essentially pure for your purposes.

You are "looking to make the perfect flakey sea salt". NaCl tends to crystallize out as cubic crystals, so you are trying to control the crystallization by means of other active agents, which might be at a very tiny concentration. Understanding the chemistry in such depth that you could publish in a respected journal would be possible, but probably not feasible, and maybe not even all that interesting.

Here's what I propose: You have some situations where you take seawater and get some desirable flakey crystals. You will also have some liquid brine left over. Is the active agent all deposited with the solid salt, or is active agent a major component, and retained in the concentrated liquid brine? Test: 1) Recrystallize the solid salt. Does it retain its flakey crystal structure, or have you fractionated the active agent into the retained liquid? 2) Take the liquid brine left over from the first crystallization, add the exact amount of ("pure") table salt that was removed, dissolve with heat, and cool to crystallize again. Do the new crystals have the flakey structure, indicating that the active agent was retained, or do you get simple cubes? The two experiments should give some idea how the active agent behaves. #2 can also be modified by adding more or less pure salt to determine how effective the active agent is in producing flakey crystals.

Hopefully, the active agent will go to one place and not the other, and you will have established some means of control that satisfies your need, For example, if all seawater has the active agent, just at slightly different concentrations, you could take your seawater, precipitate out the first (non-flakey) crop of salt, then add the liquid retained to a fresh batch of seawater and boil it down. In this way, you will have increased the level of impurities. If, on the other hand, the active agent (or lack of an anti-active agent!) has gone into the solid salt, add that to your next batch of seawater to produce flakey crystals.

Another possibility is that the flakeiness is not dependent on the analysis, but on some procedural difference (stirring, rate of temperature decrease, size of batch, seeding, some biologics that come from the seawater that do or do not decompose under your boiling down - seawater is foamy from animals living and peeing in it). In that case, even the best analytical procedures might miss the clue.

Answer 3

There's no good way to quantitatively or semi-quantitatively analyze for Na, Ca or Mg at home. You could investigate Ion Selective Electrodes and see if they'll give you the desired accuracy (ThermoFisher has Cl, Na, & Ca I.S.E.s which generally can be simply plugged in to a pH meter and then calibrated). Two other things worth mentioning: you need to filter ocean water - bacteria, algae, and all sorts of other organisms will be present in varying amounts, not to mention silt, and other colloidal inorganics. There also could be differences in dissolved gasses present. So, you need to standardize your handling of the water - from where you get it, to where and how you store it, to how you filter is, and how you process it. Don't assume that mixing it - or shaking it won't affect it. Try to figure out what you're doing to get the crystals you want. It's unlikely, imho, that the Na, Ca, Mg content varies much (although you should treat my opinion as a layman's - I've no direct experience with sea water variability.) I AM assuming you know enough to understand what near-by rivers and recent rains and obviously wind and tidal currents might do to change the composition of the surface water (not to mention air temperature and sunlight). Anyway, one of the cheapest easiest ways to determine dissolved solids is using a specific gravity bulb. (as long as temperature is held constant) You simply float the bulb into the solution and read from the scale what the density is. Finally, what container are you heating this in? Be aware that aluminum should not be used! And I'd prefer glass to stainless steel, but as long as there's no visual signs of corrosion, ss is probably ok. Also, while I'm sure you want a "natural" product, seed crystals of store-bought sodium chloride might make the crystallization more reproducible. Chemists are taught to scratch the glass side of a beaker to start crystallization. Scratches are also a site which may "catalyze" crystal formation, and since any semi-commercial (?) process can't use a new polished pan for each batch, maybe scouring the pan consistently before each batch is the way to go. HTH, these are mostly random thoughts of an industrial chemist kibitzing in an area he has little experience in.