(21) G. H. says: Please decide the following: A. claims that a team of horses can draw a greater load when hitched close to it than when hitched at a distance of 10 or 20 feet. B. claims that, everything else being equal, distance makes no difference, and that the team could pull as many lbs. at a distance of 20 feet as it could at ten or less. Which is right? A. We incline to B.'s opinion.
Please tell me the relative power of conducting electricity of the principal metals. A. According to Matthiessen, the electrical conductivity of the principal metals, under similar conditions, is as follows:
| Silver | 100.0 |
| Copper | 99.9 |
| Gold | 80.0 |
| Aluminium | 56.0 |
| Sodium | 37.4 |
| Zinc | 29.0 |
| Cadmium | 23.7 |
| Potassium | 20.8 |
| Platinum | 18.0 |
| Iron | 16.8 |
| Tin | 13.1 |
| Lead | 8.3 |
| German silver | 7.7 |
| Antimony | 4.6 |
| Mercury | 1.6 |
| Bismuth | 1.2 |
(22) S. R. S. asks: How can lime, or rather phosphate of lime, be precipitated from cod liver oil, which is perfectly clear and said to contain 2 per cent. of the phosphate? A. This can only be done by first destroying the organic matter of the oil, and then examining the residue for the phosphates with the usual reagents—magnesia solution, barium chloride, nitrate of silver, ammonium molybdate, etc. With so small a percentage of the phosphates, it will be necessary for you to work with concentrated solutions, and slowly. The oil may be oxidized by treating it on the waterbath with hot hydrochloric acid, with some chlorate of potash, added in small quantities at a time. Then evaporate down nearly to dryness, and treat with a little strong nitric and a few drops of sulphuric acid. This will take some time if properly done.
(23) J. H. S. says, in answer to J. H. B.'s query as to a parrot pulling out his feathers: Take a knife and scrape the inside edge of the bill, and the feathers will slip from the bill without coming out. This is done for feather-eating hens; no doubt it will answer for a parrot as well.
(24) S. R. S. says: I have some dentists' pellet gold. I alloyed it with brass and silver. I melted it several times, but it was so very brittle that I could not work it. I then added a $2½ gold coin, and fused, all together, but it was as brittle as before. I then fused it and dropped in lumps of pure saltpeter, but it is still as brittle as before. I fused the gold on a lump of charcoal with an alcohol blowpipe. Please tell me how to work it. A. You fail to state the proportions of your alloy. There may be an excess of zinc and copper, or the fusion may not have been complete. Place it, together with several small pieces of rosin and a little borax or carbonate of soda, in a small blacklead crucible, and heat to very bright redness over a good fire. If this does not obviate the difficulty, fuse the alloy with about three times its weight of nitrate of potassa (saltpeter), and treat the mass when cold with dilute sulphuric acid. Pour off the acid solution and fuse the alloy, together with any silver sulphate adhering to it and a little carbonate of soda. Any silver contained in the acid solution may be recovered by adding a little salt or muriatic acid, and fusing the precipitated chloride of silver with carbonate of soda.
(25) N. S. asks: 1. Can water be decomposed into its constituents (oxygen and hydrogen) with any considerable rapidity, and in large quantities, by electricity? A. Yes; providing a large magneto-electric machine be used. 2. What is the best and cheapest method of generating hydrogen in large quantities? A. The action of iron or zinc scraps on diluted oil of vitriol is among the best. A considerable volume of pure hydrogen may also be obtained with facility by passing superheated steam through a large iron tube filled with scrap iron heated to bright redness.