The construction ,of a th ermostated liquid infrared cell for
the temperature range from -1ooc to gooc is described. \u27The cell
is designed specifically for the P erkin-Elmer 21 series of double
beam infrared spectrophotometers (Perkin-Elmer 21, 221 , 421 and
521), and can be conveniently used for kinetic studies

Z . Meić

Z. Majerski

English

The construction ,of a th ermostated liquid infrared cell for

the temperature range from -1ooc to gooc is described. 'The cell

is designed specifically for the P erkin-Elmer 21 series of double

beam infrared spectrophotometers (Perkin-Elmer 21, 221 , 421 and

521), and can be conveniently used for kinetic studies

Majerski, Z.

Meić, Z .

Hrčak - Portal of scientific journals of Croatia

CCA-350 CR 0 AT IC A CHEMIC A ACT A 36 (1964) 233 545.821 :541.08 :541.124 Note An Infrared Cell for Kinetic Studies of Liquid Samples Z. Majerski and Z. Meic Institute »Ruder Boskovic«, Zagreb, Croatia, Yugosiavia Received November 5, 1964 The construction ,of a thermostated liquid infrared cell for the temperature range from -1ooc to gooc is described. 'The cell is designed specifically for the Perkin-Elmer 21 series of double beam infrared spectrophotometers (Perkin-Elmer 21, 221 , 421 and 521), and can be conveniently used for kinetic studies. Hitherto a number of infrared cells have been described1-a which are suitable for measurements of iprecisely thermostated liquid samples. The basic characteristics required for such a cell are summarized in a recent paper by Vinogradov and Crawford 1• Beside construction requirements, such as simple handling, variable sample thickness and prevention o,f evapo-ration, the greatest difficulties in operating the cell lie in temperature control and fogging of the windows below 10°C. In this paper we wish to describe a thermostated cell desigined for use with the Perkin-Elmer 21 series of doUJble beam 1spectrophotometers (Perkin--Elmer .21, 221, 421 and 521). The cell (Fig. 1) can be operated in the tempe-Fig. 1 rature range from -10°C to 90°C and is therefore particularly useful for studies of organic ·reaction mechanisms. Using this cell rate constants and activation energies can be determined. If the reaction mixture is circulated through the cell, the 'Progress of chemical reaction can be followed. 234 Z. MAJERSKI AND Z. MEIC In Fig. 2 two cross sections of the cell are presented. The body of the cell consists of two stainless steel parts (B 1 and B2) connected with a rubber gasket seal. Through the so formed jacket J the thermostated liquid circulates, entering J through the opening 0 at the lower part of the cell. The outlet is placed diagonally from the inlet. In the central part of the cell there is a bore for the light beam. The conical shape of the bore corresponds to the geometry of the beam, simplifying also the construction of the essential parts of the cell by making them smaller and reducing the transmission of heat between the instrument and the cell. The liquid sample is introduced into the space S by means of a hypodermic syringe through the opening F. The volume of the cell can be varied by using different spacers L, conveniently made of amalgamated lead foil. The spacer is tightly pressed to the cell body B1 by a polished ring R with a plug which prevents the ring from rotating and crumpling the spacer. Ring R and windows Wi and W2 are fixed by nuts Ni and N 2• Nut N 3 closes the back ·side of the cell. The sliding adapter SA with fixed metal rails and mobile Textolite sledges permits attachment of the _cell to the spectrophotometer. This adapter also makes CROSS-SECTION e-e Th / / / / / E 0 1 2 3 4 S cm Fig. 2 CROSS-SECTION A-A I Q - Sta1nlus stHl .. Rubber gask•h ~leflon eii Textolit& ~ Sodium cMorid11 ~ lru;utotion possible easy exchange of the spacer and windows (Wi and W2). At the same time the Textolite sledges serve as an insulator. The whole cell is enclosed with the insulator I upholstered by sheet aluminum. Fogging of windows W1 and W2 was observed below 150C. This was avoided by installing windows W3 and W4, and by evacuating the internal part of the cell through V. External windows W3 and W4 are fixed by holders H 1 and H2 (which at the same time serve as bearings for blowers Bl - see below). 0-ring gaskets on nuts Ni, N 2 and N3, and flat gaskets on windows Wi, W3 and W4 made it pos-sible to evacuate the cell down to 10-4mm. It should be noted that the gasket on window Wi is made of chemically resistent rubber since it contacts the liquid sample. Fogging of external windows is successfully eliminated down to tempera-ture -lOOC by purging warm dry nitrogen through blowers Bl. Nitrogen is introduced through ducts E. INFRARED CELL 235 The temperature in the cell was mea.sured by a copper-constantan thermo-couple Th using the compensation method with the reference couple in ice water. The couple wires run through a thin metal duct and holder so that their joint touches the lead spacer. The relative positions of the described coiliilections are presented on Fig. 1. As a constant temperature reservoir for temperatures b etween 20°C and 90°C a Colora ultrathermostat was used. The temperature of the circulating medium was kept constant within ±0.01°c. For temperatures below room tem-perature a Lauda ultrakryostat MK-70D with ethanol was used. The maximum variation of the temperature was ±o.1°c. The actual temperature of the thermo-stated sample in the infrared beam was measured by a thermocouple made of thin copper and constantan wires introduced into S through the opening F. 'the sample temperature was always higher than the one measured by thermo-couple Th. This difference decreased from 0.6°C at room temperature to 0.3°C at 90°C and 0.4°C at -10°C. The h1gher temperature ·Of the ,sample is probably due to the infrared radiation. The cell reaches the temperature equilibrium in about 30 minutes after connecting it to the thermostat, while the temperature of the sample is esta-blished in 2-3 minutes after inj ection. The maximum variation in the tem-perature of the cell observed during scanning (6 hous or more) was ±0.025°C when working above room temperature and ±0.075°C below room temperature. The operating temper ature range of the cell can be extended by using a higher boiling medium in the thermostat. On the other hand, lowering the temperature below -10°C is rather difficult because of more intense fogging of external windows. It might be ,possible to prevent this by better insulation of windows W3 and W4 and more efficient flushing with nitrogen so that temperatures down to about -20°C could be used. Acknowledgments. The authors are indebted to Mr. S. Ivankovic and to Mr. M. Bukovec for valuable technical assistance. Special thanks are due to Dr. D. Sunko for helpful discussions and reading critically the manuscript. REFERENCES 1. S. N. Vi no gr a do v and R. J . C raw ford, Spectrochim. Acta 18 (1962) 429. 2. J. Pow 1 i ng and H. J . B er n stein, J. Am. Chem. Soc. 73 (1951) 1815. 3. M. S. Smith and P. A. D. D e M ai n e, Can. J . Chem. 41 (1963) 812. IZVOD Celija za kineticke studije tekucih uzoraka metodom infracrvene spektroskopije Z. Majerski i Z. Meic Opisana je konstrukcija termostatirane celije za kineticka ispitivanja tekucih uzoraka metodom infracrvene spektroskopije. Celija se moze koristiti unutar tempe-raturnoga podrucja od -lOOC do 900C i konstruirana je specijalno za spektrofotometre Perkin-Elmerove serije 21 (21, 221 , 421 i 521) . Temperatura celij e stabilizira se za najviSe pola sata nakon pocetka termostatiranja i varira maksimalno za ±0.025~C iznad sobne temperature i ± 0.075°C ispod sobne temperature. !NSTITUT »RUDER BOSKOVIC« ZAGREl3 Primljeno 5. stud enoga 1964 

An Infrared Cell for Kinetic Studies of Liquid Samples

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