fused CaCl,, as a preliminary experiment. I t appeared evident, however, t h a t these results must be incorrect unless the amount of moisture in the oxide could be correctly estimated before and after the test, so as t o correct for the moisture originally contained in the oxide, and carried along by the water formed by the reaction. This is difficult, and requires time, and, owing t o the rapidity with which some oxides revivify, it is almost impossible. Without this correction the method would be lacking in accuracy to such an extent t h a t i t would be of little value, and t o avoid this the entire products must be weighed. The results obtained were very satisfactory, and the method has been in use for over a year with good results. It enables one to determine in a very short time (about I hour), whether a n oxide t o be used, is very active, active, or indifferent. The procedure is as follows: A glass tube with a bulb a t one end (see C in sketch) is most suitable to hold the oxide to be tested, but a
U-tube or almost any other tube compact enough so that i t can be weighed on a n analytical balance will answer. In tube C a ayer is placed over the outlet t o prevent any of the contents from passing through the little outlet tubing. On this cotton is placed enough small granular calcium chloride to fill the bulb; i t is then covered with a thin layer of cotton t o hold the calcium chloride in place. Five grams of the oxide t o be tested are next mixed with about 2 grams of coarse sifted sawdust and placed in the tube, and covered with another layer of cotton to prevent a n y of the contents from falling out a t the stopper end of the tube. The stopper is then inserted. The entire tube is accurately weighed and the total weight noted. A U-tube filled with calcium chloride t o dry the hydrogen sulfide issuing from the generator is connected with the test tube by means of a piece of rubber tubing and the whole connected with the generator. A small piece of glass tubing closed a t one end so as t o leave only a hole the size of a small pinhole and placed between the U-tube and the generator regulates the flow of gas. The hydrogen sulfide gas generated in the Kipp generator, and dried by passing it through the calcium chloride in the U-tube, is decomposed by the iron oxide in the test tube C, forming iron sulfide and water. The water formed is absorbed by the calcium chloride in the bulb of the test tube.
The test is carried on for I hour, after which time the test tube is disconnected and weighed. The gain in weight represents the amount of hydrogen sulfide absorbed. or rather decomposed, by the oxide. By dividing the amount of oxide taken, into this weight, the percentage of hydrogen sulfide decomposed can be determined. and from the latter the sulfur calculated. The following analysis and fouling tests made with some oxides n-ill illustrate how much more satisfactory results can be obtained by the fouling test than by chemical analysis alone. *
No. 1 Per cent
Sample S o .
No. 2 Per cent
No. 3 Per cent
No. 4
No. 5
Per cent
Per cent
. . . . . . . . . . . . . . . .47.36 64.00 65.92 72.32 76.90 . 22.01 Total H2S absorbed per unit of Fez08 4 6 . 5 After revivification ..... . , . . . . .. , . . 2 1 . 3 4
19.85 31.0 3.5
10.80 16.4 3.34
2.66 3.7 1.66
2.80 3.6 1.58
Since the above fouling tests were borne out by results obtained on a large scale in the works, one is encouraged t o believe it will greatly reduce the work of the chemist, and a t the same time give information t h a t usually can not be obtained from chemical analysis alone. Some oxides are very active a t the first fouling (when new), but revivification is slow and incomplete, and on second fouling they give far lower results. For this reason i t is sometimes desirable t o carry the test far enough t o determine the total absorbing capacity of an oxide. This is particularly the case where a new oxide is to be introduced, as well as where new shipments are t o be received. I n this case i t is advisable t o keep the CaC1, and oxide in separate tubes, but they should be weighed together. After the first fouling, the oxide tube is disconnected from the CaCI, tube. and air passed over i t until completely revivified. To prevent a n oxide which has the tendency to revivify very rapidly from getting too hot and consequently burning, thus becoming more or less inert, it is advisable t o pass the air used for revivification over water so as t o saturate i t with water vapor. After complete revivification, the tubes of oxide and CaC1, are again weighed and connected with the Kipp apparatus, and fouled a second time. This second fouling as a rule is sufficient t o show how active the material is, for if the results of the second fouling are very close to those of the first, the material is very active, but the test can be repeated the same number of times as the .oxide is revivified in practice: thus the entire capacity of the oxide can he determined before i t is placed in service. CHEMICALLABORATORY ‘CSITED G a s IMPROVEMENT Co. PHILADELPHIA
THE ELIMINATION OF RUBBER STOPPERS FROM THE VITRIFIED CLAY COMBUSTION TUBE BY MEANS OF TAPERED CLAY INLET AND OUTLET Received June 13. 1913 B Y CHAS. MORRIS JOHXSON
In THIS JOL-RNAL, 5 , 488, the writer published an account of a vitrified clay combustion tube with
vapered outlet dcsigned b y t h e author and manufactured at this works. The tube has been in successful operation for six weeks of twenty-four hour working days and is still in commission. Several more arc now in use and mark a consirierablc reduction in cost of carbon determinations a s t h e material from which the tubes are made costs less thau I cent per tuhe. T h e advantage of the tapered outlet very soon suggestcd t h e making of a tapered clay inlet which is shown at K in t h e illustration a n d also a t L-Af. The clay part of the inlet is a duplicarc of the outlet end. The tuhe is charged and discharged by re-
piercid b y t h e cylindrical surface o i the cornbustion tube which makes only a single circle o i contact between the stoppcr a n d the tubc. The slip-over gives a tangential contact which provides innumerable circles of contact. Further superiority of the tapered clay a n d rubber sleeve inlet is t h a t , should the bore of the combustion tube tend to bc elliptical instead of a true circle, t h e elasticity of the rubber sleeve will still give a pressure-tight connection on account of the large surface o i contact. Again, many combustion tubes offered b y dealers arc rejected because of grooves in the interior walls.
moving L-M which is connected t o t h e main part of t h e combustion tube by means of the rubber sleeve 3f. This connection is a piece of a/, inch bore, inches long, pure rubber tubing. inch wall a n d ,'I* This sleeve is more easily handled t h a n a rubber stopper. T h e operator grasps L-M at the clay part L a n d slips it over t h e main part o i t h e combustion tube a n d twists it firmly in place. The clay part L offers a substantial hold for one's hand a n d is absolutely safe. A glass taper would be dangerous as it might be crushed il-hen grasped, causing a wound. The slip-over connection is geomctricaily a tighter connection than a rubber stopper, for the reason t h a t t h e latter affords a n example of a conical surface
at the inlet or outlet ends, which make tight connections with rubber stoppers impossible. The tapered slipover connection renders such tubes perfectly satisfactory.
I
T h e entire apparatus with the single exception of the little mercury valve tube attached t o 1,-M is the author's design a n d shows b u t one rubber stopper at a n unimportant point in t h e little KOH drying tuhe at the extreme outlet end of the combustion train. This could also be eliminated by a small glass taper or clay taper. L*BOB*T"RY
ADDRESSES
EXPERT TESTIMONY-ITS MATERIALITY-CAUSES FOR ITS DISCREDIT-AND REMEDY' BY Jaoci. I. T. ROKALD
Expert testimony does not always consist entirely of opinions. The bacteriologist knows whether microbes are in thc water and whether germs are in the food; the toxicologist knows whether poison is found in the tissues; the metallurgist knows that certain clays contain aluminum and that it will bubble forth under certain heat; the chemist knows the results to follow certain conditions; the doctor knows the causes of many diseases and conditions: the constructive engineer knows the tensile Address delivered by Judge Ronald, of the King County Su~erior Court. before the Puget Sound Section. ? . C. S . , Ilrrch, 1913.
OP T"&
C ~ U C I B LSTBBL B co.
rAnK WORK3 01.AWERICA
1I
strength of various materials: the civil engineer hmws levels, curves and volum~of cuts and fills. All this is expert testimony, but this paper deals only with that class of espcrt testimony which consists entirely of opinions on questions of science or skill, given by persons learned or experienced therein. It constitutes the exception to tht general rule of law, that opinions are not admissible in evidence. Eminent jurists are on record in favor of the abolition of this evception.and the rejection of all opinions as evidence. This, in my opinion, would be a serious retrogression, and would result, in many cases, in excluding from courts of justice material truth, and the consequent rendition of unjust judgments based on falsehood. The field of judicial investigation, requiring the assistance
