[glot (OP)]

Need some help please. I have been trying to grow sodium chloride crystals for a while now. Trying all I can think of. I boil tap water and add table salt untill I have some on the bottom that won't dissolve. I continue to boil the water down a bit to make sure it is super saturated. I then let it cool, filter it, then let it sit for a day in a glass jar. I then hanh a rock salt crystal on a thread midway. The seed crystal disolves over a day or so. I repeat. Same thing. I have added a few crystals to the jar and they sit on the bottom for a long time. I rehang a seed and it dissolves. What am I doing wrong?

[chiralSPO]

Table salt is usually not just sodium chloride. They add other compounds to keep it from sticking together etc. Often these are not very soluble in water, so it may look like you have saturated the solution well before it is actually saturated with sodium chloride.

I have to run to a meeting now, but I will return with more advice...

[chiralSPO]

Hi Glot,

Sodium chloride is quite soluble in water, but its solubility is not very temperature-dependent. I have attached a figure I found online that shows the relationship between solubility and temperature for multiple compounds, including sodium chloride. You can see that a saturated solution at 100 °C barely has any more salt dissolved than a saturated solution at 20 °C (so this limits the amount of crystals you can hope to get.)

I think you will have better luck with either of these (try both in parallel and see which works better!):

1) Put the saturated and filtered solution in a glass jar with a few small holes made in the lid. Leave the seed crystal suspended about 2/3 of the way down to the bottom of the jar, or just wait for a nucleation to occur on the bottom. The smaller (and fewer) the holes in the lid, the slower the crystals will grow, and the bigger/better they will be.

2) Put the saturated and filtered solution in a small glass jar with no lid (fill it no more than 1/3 full). Then put this small jar inside a larger one that has methanol or acetone in it (same volume as the liquid in the small jar). Seal the large one tightly, and leave it alone until you want to harvest. The methanol will slowly evaporate and get absorbed into the water solution. Salt is much less soluble in methanol than water, so this will slowly decrease the solubility of the salt, eventually forcing a significant amount out as crystals. Again, the slower the crystals will grow, and the bigger/better they will be, in this case you can control the rate by adding some water to the methanol in the outer jar. (setup shown in another attachment--also found online).

[chris]

@glot - Can you please adhere to forum policy and reformat your post title as a question. You can do this by using the ACTION button on the post to modify the thread title so that it is compliant. Your post may be deleted otherwise.

Thank you.

[chiralSPO]

Hi Chris and Glot,

I have changed the title of the thread. In the future, Glot (and any other readers out there), when starting a new thread, we ask that the title be in the form of a question. Thank you.

[glot (OP)]

I have also tried adding rock salt to a jar of water and shaking it occasionally for a number of days until no more appeared to be dissolving. I end up with the same results. My gut feeling is I am not totally saturating the solution but why not is a mystery to me. I will give the alcohol method a try.I guess metho would be okay to use? In the past I have grown copper sulfate and Magnesium sulfate crystals quite easily. I just wanted to have my own little Halite crystal, be it manufactured. As with most science, the more that goes wrong, the more I learn.

[glot (OP)]

I made a jar of  saturated saline solution. Filtered then let stand a couple of days at room temp. Nothing. Decanted off in to another jar. Split the batch in to two smaller jars. Put a seed crystal on thread on one with a lid with lots of holes. Put the other in another jar. Spspended a similar crystal but with no lid. Filled the outer jar with metho 75 % the height of the inner jar. Put a sealed lid on the outer jar.
Results: The single jar, the seed crystal vanished. The alcoholic jar has now got crystals growing on the bottom, the thread and the seed is growing. I am amazed how well your method works.

[chiralSPO]

Glad I could help!

You might need to experiment a little to get the best crystals. Feel free to post some pix of you setup and/or the final crystals.

[glot (OP)]

This is an easy experiemnt and well worth doing. Again thanks. Here are some pics after about a week. The open jar is the one with alcohol. The green lidded one is the original solution with no crystal formation. The second lot was decanted from this jar.