1. The carcinogenicity of silica gel
I do not know whether or not you have heard that silicone is almost the same as asbestos. It is a powder of stone and has carcinogenicity. Therefore, we must warn you not to inhale your body! Xiaobian has always believed in many years, and this is actually a false news. In fact, asbestos has the same carcinogenic properties as "crystalline silica," and amorphous silica should not be carcinogenic. Japan Poison Information Center: 2 Non-crystalline silica compounds are not toxic because they are not absorbed by the body. IARC (International Agency for Research on Cancer): A crystalline silica compound corresponds to Groupe1 "having a certain carcinogenicity to humans" and an amorphous compound to Groupe3 "cannot determine whether it can be classified as carcinogenicity" (Note: "No carcinogenicity".) Because it cannot be confirmed, it is described as "cannot be classified." However, long-term inhalation of large quantities may cause pneumoconiosis (due to prolonged dust inhalation and lung accumulation of progressive and irreversible lesions in the lungs). Therefore, be sure to wear a mask when taking silicone!
2. Silica gel soluble in methanol?
When we found the pillars, a lot of white powder appeared if the amount of methanol was increased. Some people may think that this is the dissolution of silica gel, and Xiaobian has considered this for some time. However, after asking the silicone company, the answer was: "Silicone is not soluble in methanol!"
What is the white powder that appears?
To understand this thing, first of all know how to prepare the silica gel. Silica gel First, an alkali salt of silicate such as soda silicate is required to be acid-hydrolyzed so that the silicic acid terminal becomes Si(OH)2. Then wash with water to remove the acid. The obtained silica hydrosol is dried at a high temperature to obtain a dry gel, which is the silica gel that we usually use. What is eluted in methanol is a mineral component such as calcium carbonate. Because of the large amount of water used in the preparation of silica gel, and the quality of silica gel is the use of hard water, hard water contains many minerals, these minerals remain in the silica gel after the water is evaporated. Therefore, when using methanol as an eluent, some of these minerals were dissolved and precipitated during the volatilization of methanol. Therefore, the limit of the content of methanol is generally 30%. If it exceeds this value, the possibility of dissolution of white powder is high. However, some laboratory use silica gel used in the preparation process of soft water, then the mineral content is relatively small, so even if you elute with 100% methanol, there will be no precipitation of white powder phenomenon. So this can be used to test the quality of silica gel used in the laboratory.