There are several questions.

Diana3118

1. Is an hydrometer suitable for measuring the density of electrolyte in batteries? 2. What online resources do you use to order equipment or the same salt? (Will you reveal the secret?)

Jessica5016

I haven't used it, but I don't think it will be suitable. The density of seawater is a quite important parameter, and it's not worth saving on it. Some hydrometers even have corrections for density depending on the water temperature. Nowadays, a refractometer costs about 35 bucks and is convenient to use. Salt is usually bought because it is quite heavy, and transporting it from a distance is very expensive. It's also worth deciding first what kind of salt you want to use, and then you can ask where to buy it cheaper.

Stephanie9175

To the reading of the floating hydrometer, you need to add +2, then you will get the density according to the refractometer, but it's definitely better to check. As for the salt, it is sold in many places; all suppliers of marine life have it, and maybe someone among them will offer you something in private.