Sodium is a difficult ion to estimate at home. 

Since *most* sodium salts are water-soluble, [colorimetric]( or [spectroscopic]( methods are often employed, both of which I assume are not within arms' reach.

**Some alternatives:**

 1. Speaking of sodium estimation in foodstuff, it is usually determined by [Mohr's
   method]( which involves the precipitation titration of $\ce{Cl-}$ ions. **This is done under the assumption that sodium is mainly present as sodium chloride. Additionally, it will also register $\ce{Cl-}$ from other chlorides, and hence may give an elevated reading.** You *might* be able to do this at home. Here is a [page](
   to help you with the process.

 It is done in the presence of chromate ion ($\ce{CrO4^2-}$), and $\ce{Ag+}$ ions are added gradually. This precipitation happens initially:

 $$\ce{Ag+ + Cl- <=> AgCl(s)}$$

 When the solution runs out of $\ce{Cl-}$ ions, precipitation of the red-brown $\ce{Ag2CrO4}$ begins:

 $$\ce{Ag+ + CrO4^2- <=> Ag2CrO4(s)}$$

 This signals the end point.

 2. There are sodium ion meters, you can get them for ~300$.

 3. There is a volumetric estimation[1] for sodium directly, but it is not expedient to do it. It is based on the precipitation of sodium zinc uranyl acetate.


IMO it is difficult to do this as a home project, as it will require stuff that is not usually found at home.


[1] J. Am. Chem. Soc. 1931,  53, 9, 3288-3291 [DOI: 10.1021/ja01360a011](