Objective of this video is to synthesize pure silicon dioxide and solicit acid as intermediate. As reagents we will use sodium silicate and hydrochloric acid. Sodium silicate is very useful chemical and it can be found in hardware stores. As we do not know what concentration are our starting material we are going to make a small sample and then scale this up. So measure 40 milliliters of sodium silicate. To this small sample we will be adding hydrochloric acid or something what will form a sodium salt and leave silicon dioxide alone. You can probably go with X's hydrochloric acid but if you want to dry it without washing a lot of HCl gas will be produced. If you add less acid than stoichiometry Q there will be unreacted sodium silicate that may act as a cementing agent and may cause also problems. I think that a little X's of acid is the best way to go. Once again this depends on what is your expectation as what you see is definitely not the only way this reaction can be done. Using syringe measure about 15 milliliters of acid. Add it to sodium silicate solution by small portions. After each addition measure P H of the solution. Sodium silicate is strongly alkaline. You can see that immediately after addition for acid a chunk of gel formed. This is the solicic acid. Besides being the source of silicon dioxide and some health related uses there seems to be not many uses for this substance. This seems that concentration of sodium silicate was pretty high. To make this mixture workable we relied some water. We are not aiming for pure material so we add tap water. If you want pure silicon dioxide you may use only distilled water. This solution is now acidic. But as solicic acid polymerize it traps some sodium silicate so it cannot react with acid. We have to break solids to as fine pieces as possible. These bubbles are formed because I stored sodium silicate in open container and it reacted with some carbon dioxide. If you have fresh material there should be no gas evolved. As you can see by mixing things up solution is getting thicker and thicker so we have to add more water. There can be still some unreacted material but this is only a sample so we don't really care. P H level is about 6 so there is no need for any adjustments. Hey say hello to Mrs. Saladcat. For full scale process we will use 2 liters plastic bottles. To bottle we add 300 ml of sodium silicate solution. The lower the concentration of silicate the better mixing will be in less mechanical agitation will be needed. About 500 ml of water is added but we recommend at least 1 liter. Maybe even splitting silicate solution to 2 bottles. Solution is mixed well because sodium silicate has high viscosity. We use about 10 ml of acid for sample we should use at least 80 ml. I screw some math so I added only 60 ml. Oops. Hydrochloric acid is measured to over sized beaker and again added by portions and mixing the solution after each addition. This time we are non-measuring P H levels. Be aware that sodium silicate you get from hardware store may also produce CO2 dowering reaction so vinting bottle is highly recommended. The color of the mixture now is sunrhat perfect for cleaning and processing. However with high concentration big chunk of solid polymer is formed as you can see in this video. The only thing we can do with this is to dilute it down and mechanically process the solid. You may use high capacity grinder if you have one but there will be some acid which didn't had a opportunity to react to it may react with steel during processing and contaminate your product. We try gravitational filtration with no success. Maybe vacuum can help but chance of clogging the filter is very high. As we don't have grinder that can handle this amount of material we push larger chunks through about half a millimeter screen. You may use gloves in this process because of contamination of product and acid presence. This process is really messy but worked very well. The idea is to simply expose as much volume of solid to hydrochloric acid. After this step the mixture is split to three bottles. One on the left is without washing and next two are washed three times. The left bottle is cloudy and wonk settle. This may be due to unreacted sodium silicate as we used less acid than we shoelace was mentioned. In the washed material however there is sharp hedge between silica acid and water layer. This is bottle after one washing. When the silica acid settle down it has to be to stick to itself. So to remove water we simply siphon it out with some PVC tube. You may also decant water but this may be not as efficient. After washing we are left with very pure silica acid and filtration is a lot easier. Content of one bottle fills two coffee filters. Once again vacuum filtration will be much more efficient because filtrate still contain a lot of water. If you don't have vacuum source, pours man method is to squeeze filtrate to force the water out. This way most efficient method may be to use a larger sheet of cheese cloth and use that instead of coffee filters. Here we are getting rid of water. You may be careful though. If you use too much pressure you may start over again. One advantage of this method is that we are left with nice balls of silica acid that can be handled really well. To convert silica acid to silicon dioxide we must remove all water present. This simply mean to boil it off. You can use hot plate for smaller samples or ventilated oven for larger amounts. Or more stylish method. We put silica acid on few layers of aluminium foil and spread it evenly. If you didn't wash your silica acid it will contain some sodium chloride. This is not a problem in terms of purity. Removing sodium chloride from dry sand is much easier, but if you ever try to heat sodium chloride, you may find that it tends to crack and bounce all over the place. We did this drying without washing, add it was exactly what happened. So to keep at least messy at drying stage, washing is good idea. After some time this island of drying material has formed. To speed up this process a bit we crushed bigger pieces to expose as much surface area as possible to air. If you are after silica gel you may want larger chunks instead of powder so crushing may be done in dry state. If we had microscope to test material for poor sizes we may do this. There is a video to test for poor size from NERG rage. Link will be in description. However with unmicroscope this may take time and measurements and there is large room for errors as in every indirect measurements of this complexity. We are left with this much of powder after drying. Average grain size is about 0.8mm which is too big for us. This dry material is silica dioxide or simply sand. These grains are not crystalline so to get smaller grain size we can simply grind it. To limit exposure to sand dust we add a small amount of water which is quickly absorbed. After a minute or two of grinding we can see that the sand has a lot finer texture. In fact it is so fine that mixture exhibits properties of non-Newtonian fluid. The sand was washed with acid and filtered which is not shown and is dried again. When almost dry and agitated due to water evaporation it looks almost as if there is no friction. The sand is moving very rapidly and dancing around and it is not looking like it is going to stop. Very nice. Finally it is time to wait the final product. Also due to smaller amount of hydrochloric acid it is fair to calculate yield based on hydrochloric acid. With 30 grams of silica dioxide the yield is 81% based on hydrochloric acid. Most of the product was lost in washing stage infiltration. If you are more careful you may be more than 95% efficient.