This section is from the "Henley's Twentieth Century Formulas Recipes Processes" encyclopedia, by Norman W. Henley and others.
To the ordinary zinc chloride, prepared by digesting chips of zinc in strong hydrochloric acid to saturation, add J spirits of sal ammoniac and 1/3 part rain water, and filter the mixture. This soldering liquid is especially adapted to the soft soldering of iron and steel, because it does not make rust spots.
To solder zinc, the zinc chloride may be used without any spirit sal ammoniac.
Mix phosphoric acid with strong spirits of wine in the following proportions:
Phosphoric acid solution.............. 1 quart
Spirits of wine (80 per cent)............. 1.5 quarts
More or less of the spirits of wine is used depending upon the concentration of the phosphoric acid solution. When this soldering liquid is applied to the metal to be soldered, the phosphoric acid immediately dissolves the oxide. The hot soldering iron vaporizes the spirits of wine very quickly and causes the oxide released by the phosphoric acid to form a glazed mass with the surplus phosphoric acid, which mass can be easily removed.
Dissolve in hydrochloric acid: Zinc, 50 parts (by weight); sal ammoniac, 50 parts.
Hydrochloric acid, 600 parts (by weight); sal ammoniac, 100 parts. Put zinc chips into the acid to saturation, next add the sal ammoniac. Filter when dissolved and preserve in flasks.
Eight hundred parts of water with 100 parts of lactic acid and 100 parts of glycerine. This dispenses with the use of chloride of zinc.
Chloride zinc...... 1 drachm
Alcohol........... 1 ounce
As a substitute for the customary soldering fluid and soldering mediums an ammonia soap is recommended, which is obtained by the mixture of a finely powdered rosin with strong ammonia solution. Of this soap only the finely divided
rosin remains on the soldered place after the soldering. This soldering process is well adapted for soldering together copper wires for electrical conduits, since the rosin at the same time serves as an insulator.