18 A A N A L Y T I C A L C H E M I S T R Y

BURETTES Made in accordance with A.H.T. Co. Specifications

BURETTES, A.H.T. Co. Specification. Made exclusively for us, according to our specifications and designs, within tolerances for accuracy found to be reasonable for work other than that requiring the use of B. of S. Certified Burettes. A.H.T. Co. Specification Burettes have found wide acceptance and in­corporate the following features:

Stopcocks. The stopcocks are attached directly to the cylinder of the burette. Stopcock plugs are interchangeable " f " specification whenever possible, and are finished with a deep ground corrugation and rubber washer at small end. See U. S. Department of Commerce Bulletin CS21-39, "Interchangeable Ground Glass Joints, Stopcocks and Stoppers," 4th ed.

All stopcocks of these Burettes are properly lubricated and fastened in place. I t is neces­sary only to wash and dry before use. The stopcock plug need not be removed.

These Burettes are tested for leaks by immersing the lower portion, including the stopcock, in a beaker of water and applying air under pressure—15 inches of mercury—to the barrel.

All-round, fine line, white graduations. All graduations extend over half the circumference of the burette, with every fifth division extending beyond the single division, and every tenth graduation continued entirely around the burette, this method being commonly designated as "all-round" graduation. The graduation marks are carefully engraved with sharply defined but narrow lines for precise reading and accurate interpolation, and are filled with fused-in, opaque white marking compound for convenient reading.

Tapered tips. The internal diameter of the delivery tips on stopcock burettes is a gradual taper, extending from 20 to 30 mm from the end, to avoid the inaccuracy caused by suddenly constricted tips. Overall length is approximately 80 mm, with wall at the end approximately 1 '/< mm thick and carefully fire finished.

Delivery time. The delivery time of stopcock burettes is controlled between approximately 32 seconds for 10 ml burettes, and 120 seconds for 100 ml burettes. The average delivery time of the 50 ml size is 65 seconds.

Uniformity. Tubing is selected of uniform bore so that, within reasonable tolerances, the linear graduated distance on all burettes of the same capacity is identical.

Accuracy. All A.H.T. Co. Specification Burettes are guaranteed to be within the following tolerances for total capacity, i.e. twice the tolerances established by the IT. S. National Bureau of Standards for Certified Burettes, these having been established as reasonable for routine work:

Capacity less than and including:

10 ml 25 ml 50 ml 100 ml

Limi t of Error:

±0.04 ml ±0.06 ml ±0.10 ml ±0.20 ml

Percentage Error: 0.4% 0.24% 0.2% 0.2%

2400. 2404.

While the above tolerances have been adopted as the minimum for practical control of these Burettes, the actual errors will usually be found to be much less. Detailed reports of typical tests sent upon request.

Basis of graduation. Unless otherwise specified, these Burettes are graduated on the basis of the true or metric liter, which is the volume occupied by a quantity of pure water at 4° C, having a mass of one kilogram, and upon the one-thousandth part of the liter or milli­liter (ml). With a few exceptions, the true or metric liter is now accepted as the standard in all analytical work. The volume is adjusted for a temperature of 20° C.

2400. B u r e t t e s , A . H . T . Co. Specification, for p inchcock, b u t wi th­ou t p inchcock a t t a c h m e n t . C a p a c i t y , m l 25 50 100 G r a d u a t i o n in te rva l , ml Vio Vio ' f\ E a c h 2 . 3 3 2 . 9 5 3 . 5 6

2404. B u r e t t e s , A .H .T . Co. Specification, with f i n t e r changeab le s t r a i gh t glass s topcocks , size No . 2. C a p a c i t y , ml 10 25 50 100 G r a d u a t i o n in t e rva l , ml J / M VIO 1/\O VB E a c h 5 . 6 0 5 . 6 0 6 . 3 0 7 . 3 8 10% discount in carton containing IS, one size and number

only SO % discount in lots of 48 \ assorted sizes, i?i carton units SÔ% discount in lots of 144 I only.

2410. Burettes, Paired, A.H.T. Co. Specification, with Τ inter­changeable straight matched glass stopcock No. 2, exactly same as 2404, but with one stopcock placed in left-hand position and with matched total linear dimension of gradu­ated length. Not sold separately. Capacity 50 ml in Vioths. Per pair IS.75

2411. Burettes, Paired, A.H.T. Co. Specification, with angled tips and Τ interchangeable straight glass stopcock, size No. 2. Capacity 50 ml, in Vio ml divisions. Similar to 2410, but with long tips double bent to bring the outlets in juxta­position at a point approximately 4 inches in front of the burettes for insertion in the same beaker. Distance be­tween centers of burettes approximately 7Vf inches. As supplied with various Hydrogen Ion and Electrometric Titration Outfits. Per pair 24.45 10 % discount in lots of IS pairs, one number only

Detailed descriptions and prices on nine additional types of A.H.T. Co. Specification BURETTES sent upon request.

ARTHUR H. THOMAS COMPANY LABORATORY APPARATUS AND REAGENTS

W E S T W A S H I N G T O N S Q U A R E P H I L A D E L P H I A 5, PA.

Te le type Services: Western Union W U X and Bell System PH-72