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ADt 4 044L

DEFENSE DOCUMENTATION CENTERFOR

SCIENTIFIC AND TECHNICAL INFORMATION

CAMERON STATION. ALEXANDRIA. VIRGINIA

UNCLASSIFIED

NOTlCE: When oveinmnt or other drawinpg, sel-fications or other data a•e used for ny purposeother than in connection with a definitely Mlatedgvrment procurment operation, the U. S.0oveziuent thereby Incurs no responsibility, nor anyobligation whatmoever; and the fact that the Govern-ment may have formlated, furniohed, or in an wysupplied the aid drawingp, specifications., or otherdata is not to be regarded by implication or other-vim a in any manner 1l.censing the holder or anyother person or corporation, or conveying any rightsor peruission to manufacture, use or sell anypatented invention that my i any way be relatedthereto.

DISPOSITION

Destroy do not return

DISCLAIMER

The fhin.dn in this report are not to be construed asan offical Department of the Army Position.

Piestluq Arseals Tooiuioal Memwmnm. So. 1131

oil TiAT OF ~MW GLAZI (X 3131f = S12 CCSIT

by

Richard N. Abbott, Rathin N. Lisstq andMilton Rtoth

March 1963

Reviewedby t A4;•.•~ KA -,, F .HE V...Chief, Anlytioal Chemistry Sectien

Deputy Chief forPropellant Research

Approved bys MWChief, Rq1Omivos and Propoants.Laboratory

Feltma Research LaboratoriesPloati=a Arse•alDover, New Jersy

ABSTMACT I

CGCLUSIC8 2

IINTIROUCTIO 2-

MULTS AND DISCUSSIO3

EXPUInUTAL PUOCMEN

Special Apparatus 5

Special Materials 5

Determination 5-7

Not" 74

uhuu 9aa•TABLES

I. Percentages of Boron in Glasednimite Determined Under Various

Conditions. 10

II. Replicate Detezuination ofBoron Glass.

A ACT

The method described in FRL-TN-85 (1) for the deter-mination of the boron content of organoborane compounds hasbeen adapted to the estimation of the percentage of boronin boron-glazed limite igniter composition. About 6 hoursof elapsed time are required, of which 5 are working time,for the performance of a duplicate pair of runs. The averageagreement between duplicate runs is 0.04% of the sample.

3.

1. A method has been developed for determining the percentageof boron in boron-glased limite igniter composition..: (2). It iea modification of the method described in FRLM--85 (i).

-2. Approximately 6 hours are required of which 5 are workingtime, for the performance of a duplicate pair of runs. The averageagreement between duplicate runs is 0.0% of the sample.

RICONIATIM~S

1. The method described in this report should be adoptedfor the determination of the percentage of boron in boron-glazedSimite igniter Compositions.

DiThJCTIjg

The application of a glaze of boron has been found to impartimproved properties to limit. Igniter Composition. This compositionis described in Purchase Specification AE 1-54 (2) which requiresthat the glaze constitute 2 j 1% of the weight of the total material,and that the resultant glazed finish be evident on visual inspection.Needless to say, a convenient method for quantitative measurement ofthe percentage of boron represented by the glaze is much to be pre-ferred over a purely qualitative observation.

It is desirable that any method, particularly one to be includedin a specification, be reasrnably rapid and reproducible, easilyperformed, and not require h. hly specialized equipment.

2

|I

A recently-reported method for determining the boron contentof organo-borane compounds (1) appeared to satisfy these generalrequirements for a specification method and to be of very broadscope. Only a modification of the details of this method wasnecessary to adapt it to the estimation of the boron content ofthe glazed Eimite composition for which it has been found well-suited. The steps in the modification process and the finalmodified procedure are described in this report.

RESULTS AND DISCUSSION

The several steps in the adaptation of the method ofFHL-TN-85 to the analysis of boron-glazed Eimite should be apparenton inspection of Table I. As successive samples were receivedprogressive changes were made until a modified procedure had beenevolved utilizing the same principles but especially suited to theanalysis of this composition.

The often sensitive nature of the organoborane preparationsto be analyzed by the method of FEL-TN-85, and the frequentlysmall qLantities synthesized, limited the specimens to be analyzedby that method to 0.02 grams. Since the boron-glazed Eimite ex-hibits no such tendency to explosive decomposition, and since thequantity of sample submitted is generally large, it is possibleto increase the weight of specimen from 0.02 to 1 gram, with aresulting increase in titration from about 0.4 to 7 ml. of bariumhydroxide. Such a change is obviously in the interest of increased"signal-to-noise ratio".

The tendency for the apparent boron content to decrease asthe specimen weight increases indicates that there is a definitefactor of error operating which becomes relatively small and maybe neglected if the specimen taken is at least 0.3 gram.

The lower sensitivity also makes possible the eliminationof one of the more tedious steps of the FRL-TN-85 procedure -the addition of the digestion acids, milliliter by milliter, toallow time for reaction between each increment. Instead the acidsare pre-mixed and the total amount required is added in a singleportion. Unfortunately, the potassium dichromate used to signalcompletion of digestion cannot be incorporated into the acid mix-ture because of its insolubility; and therefore, must still beadded separately.

3

Mention has been made of the increased digestion temperature,indicated in Table I by the rate of reflux. In FRL-TI-85 thetemperature was limited to the low level corresponding to a dropof reflux every 5 minutes. For the analysis of boron-coated Eimiteit was found possible to increase the temperature to the maxim-attainable on a Lindberg hot plate (4 seconds per drop), withoutany tendency to decompose violently. To avoid both loss of boronand discharge of perchloric acid vapor, the digestion flask is pro-tected by an air-condenser. Pre-heating on the steam bath was testedin the case of Sample 30 but judged to be of no advantage and was notincluded in the final procedure. The treatment finally adopted con-sists of 30 minutes of heating on this hot plate with a 1/8-inchthickness of asbestos board under the flask (15 seconds per drop)followed by heating directly,./ on the hot plate (4 seconds per drop)until completion of the process is indicated by a change of colorfrom green to the orange characteristic of dichromate. The latterphase required 10-20 minutes. Although the weight of sample takenis much greater than that used in FRL-TN-85 (1 g. vs 0.02.t) theincreased temperature results in a decrease of digestion time from1*2 hours to less than an hourk..-

To estimate the precision of the procedure finally evolved,6 replicate determinations were performed on one of the samples(No. 30), with results shown in Table II. The barium hydroxide-solution was standardized for each replicate determination. Theagreement is very satisfactoryj with an average difference betweenruns of 0.04% boron. Application of a Studentized Range Table (3)shows a 95% probability that duplicate runs will agree within 0.12.In routine analytical practice, agreement would be expected to beeven better, since a common standardization would ordinarily beperformed for each series of runs, eliminating the standardizationcomponent of the error. Since the objective of the manufacturingprocess is to apply a coating of boron equal to 2 J 1% of the weightof the base grain, and since the boron used is known to be of about80% purity, the average percentage of boron found is almost exactlywhat should be expected. About six hours of elapsed time, five ofwhich are working time, are required for the performance of aduplicate pair of runs of a single sample. An economy of workingtime would result if several samples were analyzed simultaneously.

4

EEXPMEINTAL PRCER

Special Apparatus:

pH meter equipped with glass-calomel electrode system, andcalibrated with pH7 buffer.

Buret, 10 ml., graduated at 0.05 ml. intervals.

Hot plate, 2i Watts/sq. inch, Lindberg Type H-2 or equivalent.

Special Materials:

Barium hydroxide solution, prepared by steeping 3 grams ofbarium hydroxide octahydrate in a liter of water at least overnight,thm filtering through a Whatman No. 12 or equivalent folded paper.

Boric acid, standard solution containing 0.17 mg. of boronper ml., prepared by dissolving an accurately weighed 0.5 gramportion of boric acid in 500 ml. of water.

Hydrochloric acid, XN solution.

Mixed acid, prepared by stirring 33 ml. of 71% perchloricacid into 12 ml. of water, and into this, stirring 55 ml. of 96%sulfuric acid. This mixture must be permitted to cool before use.

Potassium dichromate, 2% solution.

Sodium hydroxide, 2N solution, freshly prepared.

Determination:

Accurately weigh a 1-gram specimen into a 250-ml. erlenmeyerflask with standard-taper joint and insert an air-condenser., Throughthe condenser add 1 ml. of potassium dichromate solution and, IJ10 ml. of mixed acid. Make similar additions to a sample-free blank)flask (Note 1). Heat for a half-hour at a reflux rate of 3-4 dropsper minute (Note 2), then increase the temperature to a rate of 10-15drops per minute and hold at this temperature until the color of thecontents changes from green to orange. Remove the flasks and letthem cool to room temperature. Wash the condenser walls and basewith water and transfer the contents of the flask to a 250-ml.

5

volumetric flask. Add water to bring the volume to the mark andshake to mix.

Transfer a 25-mi. aliquot from the volumetric flask to a150-ml. erlenmeyer flask with a standard-taper joint. From a10-ml. Mohr pipet, add 8 ml. of freshly-prepared 2N sodium hydroxidesolution, a strip of litmus paper (Note 3), and more sodium hydroxidesolution dropwise until the paper just turns blue. Wash the flaskmouth and walls with water. Add IN hydrochloric acid a drop at atime until the color of the litmus paper just reverts to red, and,then one drop more. Attach the flask to a water-cooled condenser,reflux for 15 minutes, then remove the flask and place it in acold-water bath (Note 4).

When cool, wash the contents of the flask into a 150-ml.beaker and insert the electrodes of the pH meter (Note 5). Fromthe 10-ml. buret add barium hydroxide solution (the volume neednot be recorded) in increments of about 1 ml. to pH 4, 0.5 ml.between pH 4 and pH 5, 0.25 ml. between pH 5 and pH 6, and 0.1 ml.between pH 6 and pH 6.7. When the pH exceeds 6.7, add only a dropat a time, allowing 30 seconds between drops, until the pH isadjusted to 7.2. Ai 5 grams of mannitol and measure the volume ofbarium hydroxide solution required to restore the pH to 7.2, addingthe solution in progressively smalier increments in the manneralready described. Standardize the barium hydroxide solution notearlier than the day before nor later than the day after that onwhich the titration was performed.

To standardize the barium hydroxide solution pipet 25 ml. of"blank" solution and 10 ml. of standard boric acid solution intoa 150-ml. erlenmeyer flask with standard-taper joint. Adjust theacidity, reflux, and titrate in the manner described in the previousparagraphs. Calculate the strength of the solution as followst

6

0-1750Wf1

8 Strength of barium hydroxide solution, mg. of boron per ml.

Where:

V Volume of barium hydroxide solution required to titratethe aliquot of boric acid, ml.

W, & Weight of boric acid in the aliquot of boric acid

solution, mg.

Calculate the boron content of the sample as follows:

1OOV SB .o~r'onh,1 2_,

'W2

Wheret

S n Strength of barium hydroxide solution, mg. of boron perMi., (see previous paragraph).

V2 a Volume of barium hydroxide solution required to titratethe aliquot of sample solution, ml.

W2 a Weight of sample represented by the aliquot taken, mg.

Notes:1. It is not necessary to include a blank with each run of

samples. Blank solution from a recent (within a few weeks) run maybe used provided that the quantity on hand is sufficient to standardizethe barium hydroxide solution.

7

2. These temperatures may be attained on a Lindberg Type H-2electric hotplate, first with and then without a thickness of 1/8"asbestos board.

3. If the paper should assume the blue shade, wash down theflask and reacidify with iN hydrochloric acid solution as describedsubsequently. In later runs decrease the volume of X1 sodium hydroxidesolution added at this point.

4. A vessel containing dry ice in contact with water makes asatisfactory bath.

5. The use of a magnetic stirrer will facilitate subsequentoperations. In the event that such a stirrer is used the housing ofthe motor and the shielding of the pH meter should both be connectedto ground.

8

1. U.N. Abbott, N.V. Liszt, and U. Roth, "Estimation ofthe Boron Content of Organo-Decaborane Compounds". TechnicalNote F1•mTN-85, Picatimiy Arsenal, Dover, New Jersey,September 1961.

2." Purchase Specification AS 1-54 (Rev. i), PicatinnyArsenal, Dover, New Jersey, 16 August 1960.

3. C.A. Bennett and N.L. Franklin, "Statistical Analysisin Chemistry-and the Chemical Industry". John Wiley & Sons,Incorporated, New York, 1954, Table 5.8.

9

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DIST1IMIOUT LIST

Commanding GeneralU. S. Army Materiel CoinandATTN: ANCiUD-S - Mr. J. Crellin 1

A4CRD-RS - Mr. J. Chalmers 2Washington 25, D. C.

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Redstone Arsenal, Alabama

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Section, 1331 14Philadelphia 37, Pennsylvania

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Commanding OfficerOffice of Naval Research1030 E. Green StreetPasadena 1, California 42

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British Defense StaffBritish EmbassyATTN: Scientific Information Officer 70-733100 Massachusetts AvenueWashington, D. C.

Defense Research MemberCanadian Joint Staff (W)2450 Massachusetts AvenueWashington 8, D. C. 74-77

iti

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