13

You ask: Can I roughly get the weight that a fraction of a gram without buying a scale just for this crystal making kit? Absolutely. You're in Japan. You have access to Japanese coins which conveniently are just what you need for this project. Because they are currency, you can also be assured that they weigh exactly as advertised. You need one each of 5-...


8

I think the mass of the seed is not critical. But you can create your own scale - or even better, involve the son in its creation. You can create a 2-shoulder scale, with 2 stuff holders hanging at equal distances from the central holding. Or, you can create a 1-shoulder scale, with the stuff holder hanging on some elastic string or wire. For a scale weight ...


7

If you know the density of the crystal (usually a salt), you can estimate the mass of a crystal based on its volume, i.e. by measuring the lengths of its sides. For example, table salt (sodium chloride) has a density of $\rho=2.16\ \mathrm{g\ cm^{-3}}$. Thus a cube of $10\ \mathrm{mm}\times10\ \mathrm{mm}\times10\ \mathrm{mm}$ has a mass of about $2.2\ \...


3

The problem with H2S is that it is both highly toxic (albeit not quite at the level of HCN but surprisingly to me, too close) and with uncommon properties such as at a threshold of exposure, a suppression of the ability to detect any smell. The latter is particularly pernicious as one can, apparently, achieve a toxic dose while not even realizing that one ...


2

Yes, this is mass concentration, reporting concentration by weight. E.g., Oxy/OxyChem's documentation Hydrochloric Acid Handbook (link to pdf file), edition 08/2018 explicitly states how the two relate to each other on page 6 with: «OxyChem produces and markets Technical Grade hydrochloric acid in two concentrations: 22° Baumé (35.21% HCl by wt.) and 20° ...


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