134 



POPULAE SOIEN'CE NEWS. 



[September, 1888. 



specific gravity of any liquid can be ascertained 

 without calculation or any apparatus other than a 

 good balance and accurate weights. 



It is known that the weight of a body is to Its 

 specific gravity as its loss of weight when immersed 

 in a liquid is to the specific gravity of that liquid. 

 For example, 200 grains of citric acid (specific 

 gravity, 1.60) lose in weight 11.5 grains when 

 weighed in oil; and as 200 is to 1.60, so is 115 to 

 0.920, the specific gravity of the oil. Now, if we 

 make the weight of the citric acid the same number 

 of grains as its specific gravity, our formula be- 

 comes, as 1.60 is to 1.60, so is the loss in weight 

 of the citric acid when weighed in oil to the specific 

 gravity of the oil; or, in other words, the loss of 

 weight is equal to the specific gravity, from which 

 we deduce the following general rule: — 



The specific gravity of the liquid is equal to 

 the loss of weight (in grains) sustained by a solid 

 body when immersed in the liquid, the weight of 

 the solid being equal (in grains) to its specific 

 gravity. 



Hence it is necessary only to weigh the solid in 

 the liquid, and its loss gives at once the specific 

 gravity of the liquid. 



Taking the preceding example, if 200 grains of 

 citric acid lose 115 grains, 1.60 grains will lose 

 0.920 grain; and this loss is equal to the specific 

 gravity of the oil. 



In practice the weight of the solid might be ten 

 or a hundred times the weight of its specific gravity, 

 care being taken to put the decimal point in the 

 right place in the final result. 



As perhaps one of the most desirable solid bodies 

 to use, I would suggest a piece of aluminium 

 weighing 256 grains, the specific gravity of that 

 metal being 2.56. If, upon trial, its specific gravity 

 should vary from these figures, its weight should 

 be made to correspond. 



For liquids having greater specific gravity than 

 2.56, it would be necessary to use a heavier solid 

 than aluminium. — Alfred B. Taylor, in 

 American Journal of Pharmacy. 



THE STOLEK SECRET OF MAKING CITRIC 

 ACID. 



The following anecdote is told in the English 

 Mechanic: There used to be, close to Temple 

 Bar in London, an old chemist's shop. The 

 proprietor of it, in days gone by, enjoyed the 

 monopoly of making citric acid. More favorably 

 circumstanced than other secret manufacturers, his 

 was a process that required no assistance. He 

 employed no workmen. Experts came to sample 

 and assort and bottle his products. They never 

 entered the laboratory. The mystic operations 

 by which he grew rich were confined to himself. 

 One day, having locked the doors and blinded the 

 windows sure, as usual, our chemist went home. 

 A chimney-sweep, or boy disguised as such, wide 

 awake in chemistry, was on the watch. Following 

 the secret-keeper so far on his way to Charing 

 Cross as to be sure he would not return that day, 

 the sooty philosopher hied rapidly back to Temple 

 Bar, ascended the low building, dropped down the 

 chimney-flue, saw all he wanted, and returned, 

 carrying with him the mystery of making citric 

 acid. The monopoly of the inventor was gone. 

 A few months after, and the price was reduced by 

 four-fifths. The poor man was heart-broken, and 

 died shortly afterwards, ignorant of the trick by 

 which he had been victimized. Like Miss Tabitha 

 Bramble when informed that the thunder had 

 spoiled two barrels of beer in her cellar, he might 

 have said, "How the thunder should get there 

 when the cellar was double-locked, I can't under- 

 stand." , 



VERIFYING GRADUATED GLASS TUBES. 



M. Berthelot describes (Compt. Rend.) a 

 method employed by liim in verifying tlie gradua- 

 tion of glass tubes employed in gas analysis, which 

 is, however, equally applicable to any graduated 

 tube or burette. 



The author fills the tube with mercury when in 

 an upright position, the closed end being down- 

 wards, until it overflows, taking care that no aii- 

 bubble is introduced. A small, flat piece of glass, 

 ratlier thick, is pressed down upon the open end of 

 the tube, which is then inverted. The whole — 

 tube, mercury, and glass plate — is then weighed 

 on a balance sensitive to 0.01 gram or beyond. 

 When this is done, the arrangement is taken out, 

 and placed above a small capsule, and one corner 

 of the glass plate is raised slightly, so as to permit 

 a certain quantity of air to enter, and a corre- 

 sponding quantity of mercury to escape. The con- 

 tact of the plate and tube is re-established, the 

 arrangement is placed upright on a large horizon- 

 tal plane, and the graduation corresponding to a 

 horizontal plane tangential to the surface of the 

 meniscus is read off with a lens. lie then weighs, 

 as may be most convenient, either the mercury 

 which has escaped into the capsule, or the entire 

 system formed by the tube, the mercury, and the 

 plate, which gives the mercury escaped by differ- 

 ence. This weight, divided by the exact density 

 of mercury at the temperature of the experiment, 

 furnishes with great precision tlie volume of the 

 entire space now occupied by air and limited to 

 the graduation. In this manner the graduation of 

 any tube may be verified, and a table of correction 



drawn up. 



— ♦— 



AN EXPERIMENT TO ILLUSTRATE 

 QUANTIVALENCE. 



Lepsius has contrived a lecture apparatus for 

 demonstrating the valence of the metals, based 

 upon the method adopted by Nilson and Petterson 

 to determine the atomic weights of the rare ele- 

 ments; i. e., heating a weighed quantity of the 

 metal in dry hydrogen-chloride gas, and measuring 

 the hydrogen set free. In a combustion tube 40 

 centimeters long, pieces of thallium, of zinc, and of 

 aluminum are placed, about 10 centimeters apart; 

 the weight in each case corresponding to double 

 the atomic weight in milligrams: i.e., 408 milli- 

 grams thallium, 113 milligrams zinc, and 54 milli- 

 grams aluminum. The hydrogen chloride is evolved 

 by the action of strong sulphuric acid on a piece 

 of ammonium chloride, and is carefully dried by 

 passing it through sulphuric acid. The hydrogen 

 is collected in an apparatus like a Hofmann appa- 

 ratus for decomposing water, but which has three 

 graduated tubes, the whole rotating in a socket 

 containing mercury, so that the gas may be sent 

 into either of the tubes at will. The three tubes 

 are filled with a dilute soda solution. In perform- 

 ing the experiment, the thallium is first heated 

 with a Bunsen burner, and the hydrogen collected 

 in one of the three tubes. Then the zinc is simi- 

 larly heated, and after that the aluminum; the 

 evolved gas being collected in the second and third 

 tubes. The hydrogen in the first tube will occupy 

 22.32 cubic centimeters; that in the second, 44.62 

 cubic centimeters; and that in the third, 67.86 

 cubic centimeters: the ratio of the three being 

 1: 2: 3, or that of the valence of the metals used. 

 — American Journal of Science. 



LABORATORY NOTES. 



Estimation of Potassium in Presence ok 



SuLi'HATE.s. — E. Bauer recommends to determine 



fir.st the quantity of sulphuric acid in the sample, 



and then to add the equivalent quantity of baryta 



.solution. The filtrate is then fit to be tested for 

 potassium with platinic chloride. 



Bismuth Test. — Mr. F. 15. Stone states that 

 bismuth in very dilute solution, with a very minute 

 amount of free sulphuric acid, with a strong 

 solution of potassium iodide dropped into it, pro- 

 duces a bright-yellow color, and that this reaction 

 will show when the bismuth salt is only one part in 

 a million. 



A Quick Filter. — Take a clear piece of cham- 

 ois skin, free from thin places: cut it of the desired 

 length; wash it in a weak solution of salsoda or 

 any alkali, to remove the grease, and rinse thor- 

 oughly in cold water before using. Tinctures, 

 elixirs, sirups, and even mucilages, are filtered 

 rapidly. A pint of the thinnest sirup will run 

 through in four or five minutes. By washing 

 thoroughly after each time of using, it will last a 

 long time. 



A New Support for Funnels. — Mr. Meurer 

 describes a new support for funnels while drying. 

 It is made in the following manner: Two hori- 

 zontal parallel bars of glass tubing are supported by 

 pieces of glass rod which have their ends bent up- 

 wards till they nearly meet, and thrust into the 

 ends of the tubes, which are bent downwards at 

 right angles. A small hook of glass rod prevents 

 the bars from springing apart under the weight of 

 the funnels which rest between them. 



Porcelain Shot. — Under this name small white 

 globules of porcelain are made in Munich. They 

 are made to take the place of ordinary lead shot 

 used for cleaning wine and medicine bottles, as 

 porcelain is entirely free from the objection of pro- 

 ducing lead contamination, which is often the resul 

 when ordinary shot is used. Their hardness and 

 rough surface, producing, when shaken, greater 

 friction, adapt the porcelain shot well for quickly 

 cleaning dirty and greasy bottles ; and, as they are 

 not acted upon by acids or alkalies, almost any 

 liquid can be used. 



A New Source of Hydrogen Gas for ex- 

 perimental purposes has been pointed out. It con- 

 sists of powdered slacked lime and iron filings. 

 When these two substances are intimately mixed 

 and heated to redness in a proper container, a very 

 considerable amount of hydrogen is evolved. The 

 only precaution necessary is, to use a vessel so 

 shaped that the water of condehsation will not fall 

 or fiow back upon the material. For experimental 

 purposes a strong soft-glass tube, with a bulb blown 

 at one end, answers very well. The open end must 

 be directed downward in such manner that the con- 

 densation water will be carried off, as noted above. 

 From 20 grams of an equal mixture of lime and 

 iron filings, Stolba obtained, in the course of twenty 

 or thirty minutes, 1,230 cubic centimeters of 

 hydrogen. 



Curious Formation of Crystals. — If a 

 lump of pure granulated chloride of ammonium 

 be carefully introduced into a solution of nitrate of 

 lead, best in a wide-mouthed bottle, there will soon 

 appear pillars of crystals, resembling in some re- 

 spects the amorpho-crystalline appearance of com- 

 mercial starch, or, more accurately, angular snow- 

 banks. The result is very beautiful, but, besides, 

 affords an excellent opportunity to notice the mode 

 of formation. The minute crystals of chloride of 

 lead will be seen to rise from all sides, at the base 

 of the forming pillars, and, ascending above their 

 summits, will describe an inward curve, and fall on 

 top. The process being continued, the pillars will 

 rise rapidly. This is interesting as bearing on the 

 causes of crystalline form. If commercial fibrous 

 chlorides of ammonium be used instead of that 

 described, the result is extremely remarkable from 

 an artistic point of view, but does not show the 

 currents so distinctly. 



