The Fixing Solution. Still, the beautiful, delicate image which the developer brings forth would be fugitive, and disappear when exposed to the light, were not a fourth solution appealed to to fix it. This may be a saturated solution of hyposulphite of soda in water, or of cyanide of potassium, say one ounce to six ounces of water. The last is a deadly poison, and should never be used. The "hypo." solution should be changed frequently to avoid the creation of pin-holes upon the plates. The old, used solution contains considerable silver, and should be saved and sent to the refiner for reduction.