In order to filter the maximal amount of fluoride and arsenic from tap water or Silicade, the water must be adjusted to pH 4.8 with sodium bisulfate and then filtered slowly (i.e. less than 400cc/min) through a bone char filled filter cartridge and finally brought to pH 6.5 with sodium bicarbonate prior to drinking. The flow should be bottom-to-top in order to flush most of the air out of the bone char. The least expensive and most convenient way of constructing such a filter is to purchase an Aquatic Life ion exchange cartridge filter with quarter inch polyethylene tubing from Amazon. Pour out the ion exchange resin and fill the empty filter cartridge with bone char. The filter can be held vertically with two clamps attached to a lab stand (see figure 37). More details are given below.