Oct., 1919
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
Hydrogen of approximately t h e same purity (99.97 per cent hydrogen) was prepared in t h e same Kipp from J. T. Baker’s “C. P.” zinc said t o contain a trace of arsenic and antimony.
963
The apparatus is designed t o meet the requirements for these three determinations. APPARATUS
To set up t h e aprzratus the following material is necessary: SUMMARY I-Double burette stam,. A generator is described with which hydrogen 2-TWO certified burettes, 30 cc. capacity, graduated t o 0.05 cc. containing not more t h a n I part in 10,000 of im3-Capillary glass tubing, I t o 2 mm. inner diameter. purities can be prepared from zinc and acid. Methods 4-Four glass T tubes: Three, inner diameter 3 mm. One, of testing for contaminating gases are described. inner diameter 4 mm. The relation between t h e volume of gas generated and 5-Red rubber tubing, inner diameters of I to z mm. and also purity of t h e product is given by a n equation which 4 mm. was verified experimentally. 6--Pinchcocks, three plain and one special two-way cock. 7-Adhesive tape. BUREAU O F STANDARDS WASHINGTON, D.C. Fig. I shows the apparatus as completed and in running order in the laboratory. The burette on the AN APPARATUS FOR RAPID GASTRIC ANALYSIS right is connected TOGETHER WITH A METHOD FOR THE t o the alkali reserPRESERVATION OF STARCH SOLUTION voir, t h a t on t h e By RAYMOND J. MILLER left t o the thioReceived h’ovembrr 29, 1918 sulfate. At t h e top Considerable of the success accomplished along t h e of t h e burettes is line of gastric investigation conducted a t t h e Jefferson placed a n arrangeMedical College recently is due to a n apparatus de- ment which is signed by one of t h e members of the research staff, shown in detail in t h e author of this contribution. With t h e aid of this Fig. 2 . Near the appas-atus t h e manipulation of different solutions used base of t h e burette i n t h e several analyses has been shortened. The stand two devices apparatus demonstrates its real value not in t h e hand- will be observed. ling of one case for analysis but rather when three or The one on the more are t o be run. right leading t o the tip of t h e alkali burette is an automatic pipette used in the formol titration, and is shown in detail in Fig. 3. The attachment on t h e left leading t o t h e tip of the thiosulfate burette is an ordinary FIG.2 gravity device for the rapid addition of starch solution. Fig. z illustrates t h e overhead arrangement whereby t h e burette can be filled by suction and when t h e same is released any excess solution drawn over is immediately withdrawn back into the reservoir, leaving t h e burette reading 0.00 cc. FIG. 1 Fig. 3 shows the automatic pipette which, as soon a-Alkali Burette d-Syphon Device (Starch) as its charge is delivered, automatically fills up t o b-Thiosulfate Burette e-Formation Reservoir approximately its former level and is again ready t o c-Automatic Pipette +Starch Solution be discharged. The principle upon which this deI n gastric analysis as conducted in this laboratory vice depends is a two-way pinchcock as illustrated a t t h e following determinations are considered of most A, Fig. 3. This type pinchcock was designed by importance: another author and reported some time since. Very little has been said in regard t o the assembling I-Total Acidity: Titration with N / I O Opotassium hydroxide. z--.Free Acidity (Sahli Method) : Titration with N / I O O of material for t h e several devices as i t has been taken for granted t h a t the figures are self-explanatory. Persodium thiosulfate, finishing with starch solution. 3--.Formol Titration or Amino Acid Nitrogen Complex : haps but one thing needs an explanation and t h a t is the purpose of t h e adhesive tape. It will be observed Addition of neutral formalin and titrating with N l i o o potasin Fig. I t h a t the automatic pipette c and the starch sium hydroxide.
9 4
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
dropping device d are attached directly t o the upright support of the burette stand. Adhesive tape was found t o be the best means of fastening these devices t o the support. STARCH S O L U T I O N
The delicacy of starch solution as an indicator for iodimetric and thiosulfate titrations is well known. Its rapid deterioration, mainly due to the presence of molds, has thus far required the observation of the following precautions in its preparation: I-That the starch solution be made up fresh each day. 2-That the cold starch solution be placed in small bottles, sterilized for z hrs. on a water bath a t IOO’, closing with soft sterilized stoppers and keeping the individual bottles to be opened as the occasion required (Stokes). 3-That preservatives be added. Of these the following have been used: Mercuric iodide (Gastine); potassium chloride, saturated (Bang); potassium iodide; zinc chloride; chloroform; etc.
I n pursuance of gastric investigations in the department of physiological chemistry of t h e Jefferson Medical College, the problem of preparing a starch solution which would remain intact over a considerable period of time with as little addition of foreign material as possible was studied by the author. As a result the following procedure was developed for use in the laboratory in connection with the determination of free acidity of gastric juice by the Sahli method. Rub up in a .-.mortar, with suffi.-.cient cold distilled water t o form a paste, I O g. of soluble starch (Lintner). Boil z 1. of distilledwaterfor 1 5 FIG. 3 min. To approximately 750 cc. of the boiling water add the starch paste and stir thoroughly, Continue heating for I O min. Place the hot solution in a clean graduated cylinder and make up t o a liter with the remainder of the boiling water. Rinse the flask t o be used as a reservoir with scalding water as wellIas the siphon device (see Fig. I). Immediately place the hot starch solution in the reservoir, I cc. of toluol may or may not be added. If it is added, i t is well t o shake or stir the solution throughout. Immediately float a layer of liquid
‘’
Vol.
TI,
No.
IO
petrolatum, ‘/4 in. deep, over the surface of the hot solution. Place the short leg of the siphon device in position within the reservoir. Carefully charge the siphon with the pinchcock open. When so charged the siphon is in running order until the reservoir becomes practically “dry.” The addition of toluol t o the solution, i t is believed, can readily be omitted and is added only t o ensure a preservation of the solution in the siphon during the first usage of the starch solution. I n Fig. I i t will be noticed t h a t the end of the short leg of the siphon is bent upward. The object of this is t o avoid disturbance of the layer of residual dextrin (Blake) which generally sediments a t the end of 24 hrs. standing. This starch solution used in this apparatus has been found t o give no trace of reddish coloration with iodine for a period of 6 mos. A further study of the solution was rendered impossible because of the exhaustion of the reservoir supply. Aside from the saving of valuable time by using the above procedure, the fact t h a t starch solution having practically the same properties as a freshly prepared one with little or no addition of foreign material, was always a t hand, was of great importance. JEFFERSON MEDICAL COLLEGE PHILADELPHIA, PA.
RAPID AND CONVENIENT METHOD FOR THE PREPARATION OF CONDUCTIVITY WATER1 By C. B. CLEVFNGER Received April 5 , 1919
The frequent and increasing need for good conductivity water makes it highly desirable t o have a convenient method for its preparation. A description of such a method is especially important because some of the procedures in use are unsatisfactory in one or more respects. The apparatus used in this laboratory is a modification of the one first described by Bourdillon.2 It was originally used here by Dr. S. F. Acree but without all of the present features. The improvements a n d t h e non-acquaintance of many chemists with this still give occasion for this publication. According t o Kendall,3 with the exception of some high dilution experiments noted by himself4 and Washburn,5 the purest distilled water, after exposure t o t h e atmosphere, has a conductivity which is practically accounted for by the carbon dioxide t h a t is absorbed under atmospheric conditions. Kendall found t h a t the conductivity values of water in equilibrium with the air ranged from 0.75 x IO-^ t o 0.90 X IO-^ reciprocal ohms a t 2 5 ’ C. It is, therefore, futile t o prepare and use water having lower values than t h e above unless it is carefully protected from the carbon dioxide of the air a t all t;mes. I t is only for conductivity measurements of the greatest precision t h a t 1 Published by permission of the Director of the Wisconsin Agricultural Experiment Station. 2 Trans. J . Chem. SOL, 103 (1913), 791. 3 J . A m . Chem. SOC.,38 (1916), 1480, 2460. 4 I b i d . . 39 (1917), 7 . 6 I b z d . , 40 (1918), 106
