X-Ray Dose Determinations with Chloral Hydrate

The radiation chenlistry of aqueous solutions of chloral hydrate and of bronlal hydrate has been further investigated. T h e electrical conductivity method of Andrews and Shore (1) was used to follow the appearance of acid. T h e yield of acid was found to be dependent on the dose rate, contrary t o the conclusion reached by Andrews and Shore but in agreement with the results of other workers. A reexamination of Andrews and Shore's paper indicates that a n incorrect interpretation was made of their data and reveals that, in fact, their data also indicate a dose rate dependence for the yield of acid. A free radical mechanism is proposed which is in good agreement with the obscrved dependence of the rate of formation of acid upon the dose rate and upon the solute concentration in both the presence and in the absence of oxygen.Several reports have been published on the radiation chemistry of aqueous solutions of chloral hydrate (1-6) and of bron~al hydrate (6-11). There is general agreenlent that one of the main products is the corresponding hydrohalic acid. In the earliest reported work, that of Andrews and Shore (1) on aqueous chloral hydrate solutions, the appearance of hydrochloric acid was followed by ineasureinent of the electrical conductivity of the solution. A siinilar method was used by I-Iilsenrod (4). In the other worlr referred to, the production of acid was followed by titration with standard base. Andrews and Shore (1) interpreted their results in a manner which indicated that theG value (number of illolecules of product per 100 eV of energy absorbed) of I-IC1 was independent of dose rate. I-Iilsenrod (4) did not investigate the dose rate dependence. In contrast, all of the other worlters (2, 3, 5 , 6) reported a dose rate dependence, the G value being approxiinately inversely proportional to the square root of the dose rate. A siinilar dose rate dependence was found for aqueous solutions of broinal (6-9).No satisfactory explanation for this large discrepancy in the dose rate dependence has been offered. While.it seeins unliltely, a possible explanation is that the different behavior reported arises because of the methods used to follow the appearance of the hydrohalic acid. The electrical conductivity method is not very specific, since the appearance of any electrolyte will result in an increase in electrical conductivity. The titration nlethod is more specific, since it will respond only to acidic products. I t should be noted that Andrews and Shore (1) did do sonle chloride analysis and PI-I measurements which indicated that the electrical conductivity measured by t h a n was due mainly to hydrochloric acid. By titration with a base, they found that the anlount of total acid present was solnewhat larger than that which would be expected if only hydrochloric acid was responsible for the electrical conductivity. Similarly, Woods and Spinks (7), and I-Ieusinger et al. (8)

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“…I:rom the FIG. 1. Relation between specific co~lductance and acid concentration: 0 hydrochloric acid solutions;…”

Section: Resultsmentioning

confidence: 99%

The Radiation Chemistry of Aqueous Solutions of Chloral Hydrate and of Bromal Hydrate

McIntosh¹,

Eager²,

Spinks³

1964

Can. J. Chem.

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“…11) and tribromoethar~ol and by about for solutions of clibromoacetaldehyde, showing that besides hydrobromic acid appreciable quantities of other strongly acid products are formed from these compounds; these products are probably bromine-substituted acetic acids. I t has been reported that the yield of acid from aqueous solutions of chloral hydrate is about : 3OyO greater than the yield of chloride when they are irradiated with either Coca gamma rays (12,13) or SrgO beta rays (13). No systematic attempt has been made to determine niealtly acicl products from our irradiations; a single determination of the acid formed from a solution of bromal hydrate (1020 rads/min) using both bromophenol blue ancl bromocresol purple as indicators gave a 1'7y0 greater yield with the latter inclicator; carbon dioxide was removed from the solution before titrating.…”

Section: Ilcid Yield F R O M Air-saturated Solz~tionsmentioning

confidence: 99%

“…This Inay be largely overcome by using dilute aqueous solutions of organic halogen co~npounds, for example, chloral hydrate (12). T h e Can.…”

Section: Orgaizic Iialogen Compoz~nds I N Dosimetrymentioning

confidence: 99%

“…Acid formed from the non-polar compounds when they are irradiated in aqueous solution can be determined conveniently from the electrical co~lductivity of the solution (12,15). By this means the acid formed can be measured continuously, a t a distance, while an irradiation is in progress and the integral dose confirmed after the irradiation by titrating the acicl formed.…”

Section: Orgaizic Iialogen Compoz~nds I N Dosimetrymentioning

confidence: 99%

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The Radiolysis of Some Organic Halogen Compounds in Aqueous Solution

Woods¹,

Spinks²

1960

Can. J. Chem.

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“…I n 1950 Andrews and Shore (1) reported that aqueous chloral hydrate \vas decomposecl by X rays to yield I-ICI and other products. The acid yield, measured conducto~netrically, \vas found to be linear with radiation dose, and to increase with increasing te~nperature ancl initial chloral hyclrate concentration, but was reported to be independent of dose rate.…”

mentioning

confidence: 99%

IRRADIATION OF AQUEOUS CHLORAL HYDRATE WITH Sr⁹⁰–Y⁹⁰ BETA RAYS

Platford¹,

Spinks²

1959

Can. J. Chem.

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.Air-saturated aqueous chloral hydrate has been irradiatcd with bcta rays and the acid ) ield as determined by titratio11 has been s t~~d i e d as a f~~n c t i o n of dose rate, temperature, and initial concelitration of the chloral hydrate.The a\,erage lifctimc of the intertiiediates has been found, by Ineans of thc rotating sector technique, to be about 0.5 secolitl. Propagation and termination rate collstants for the reaction have been calculated and ari ettort has becn made t o explain the r c a~~l t s obser\,ed in terms of a free radical chaili rcactioli.I n 1950 Andrews and Shore (1) reported that aqueous chloral hydrate \vas decomposecl by X rays to yield I-ICI and other products. The acid yield, measured conducto~netrically, \vas found to be linear with radiation dose, and to increase with increasing te~nperature ancl initial chloral hyclrate concentration, but was reported to be independent of dose rate. Because of the large acid yielcl, these workers used the system as a sensitive radiation dosimeter.Freeman et al. in 1953 (2) irradiatecl the same sj.stem with CoGo y-rays and found essentially the same results as A~ldrews and Shore except that they found the acid yield to be dependent on (dose Freeman also found the racliation yield in air-free solutions to be about one fifth of that in aerated solutions.Andrews et a/. (3) have used a n agar gel containing chloral hydrate and ~nethyl red as a dosimeter for Van de Graaff electrons.I n the present work the decomposition of chloral hydrate by beta says is colnpared with that resulting from gamma rays. I.:SPEKIi\IESTr\L I pparatl~sIrradiations were carried out with a 40-mc SrgO-Ym medical applicator. The activity was confined to a n area of 1 cm%and was plated on one face of an aluminum disk to the back of which was attached a rod serving as a handle. Solutioils were irradiated in 10-ml pyrex beakers immersed in a thermostat, above which the source was suspended. The dose rate received by the solution was controlled by varying the separation between source and solution.A rotating sector with a 1ight:dark ratio of 1 : 2 was constructed from brass of thickness 1335 mg/cm2. The sector was driven through a reduction drive by a 240-r.p.nl. synchronous motor.iVIateriads All chemicals were reagent grade or better; the chloral hydrate was Fisher U.S.P. grade. All water was distilled once from alkaline permangallate and once from acidic dichromate solution. Procedure'The reaction was followed by titration of the acid produced on irradiation. Samples l.lIunz~script received February 9, 1959. Conlribtrtion froriz the

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X-Ray Dose Determinations with Chloral Hydrate

Cited by 24 publications

References 2 publications

The Radiation Chemistry of Aqueous Solutions of Chloral Hydrate and of Bromal Hydrate

The Radiation Chemistry of Aqueous Solutions of Chloral Hydrate and of Bromal Hydrate

The Radiolysis of Some Organic Halogen Compounds in Aqueous Solution

IRRADIATION OF AQUEOUS CHLORAL HYDRATE WITH Sr⁹⁰–Y⁹⁰ BETA RAYS

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X-Ray Dose Determinations with Chloral Hydrate

Cited by 24 publications

References 2 publications

The Radiation Chemistry of Aqueous Solutions of Chloral Hydrate and of Bromal Hydrate

The Radiation Chemistry of Aqueous Solutions of Chloral Hydrate and of Bromal Hydrate

The Radiolysis of Some Organic Halogen Compounds in Aqueous Solution

IRRADIATION OF AQUEOUS CHLORAL HYDRATE WITH Sr90–Y90 BETA RAYS

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IRRADIATION OF AQUEOUS CHLORAL HYDRATE WITH Sr⁹⁰–Y⁹⁰ BETA RAYS