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Ch_28_F

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Determination of Relative Humidity by Sling Psychrometer

EXPERIMENT

111

28

DETERMINATION OF RELATIVE

HUMIDITY BY SLING

PSYCHROMETER

AIM

To determine the relative humidity by wet bulb depression method using sling psychrometer.

REQUIREMENTS

Sling psychrometer

(1)

Humidity chart (wet bulb depression Chart)

(1)

PRINCIPLE

(Refer the previous experiment).

In this experiment relative humidity is determined by sling psychrometer. It consists of two thermometers fixed on a metallic frame (Refer the Fig. 28.1) which can be rotated by a handle. One of the thermometers (wet bulb) is covered with cloth sack which can be dipped in water. (See the Fig. 28.1) the second thermometer (dry bulb) is free and exposed to the air. The sling psychrometer is whirled for some seconds until the reading in the wet bulb thermometer reaches equilibrium. After reaching equilibrium it is noticed that the reading in the wet bulb thermometer is always lower than the dry bulb thermometer. The amount of cooling at the wet bulb and the fall in the reading depends upon the rate of evaporation. The rate of evaporation interns depends on the relative humidity of the air.

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Ch_29_F

P.S.Sona Laxmi Publications PDF

114 A Practical Manual of Pharmaceutical Engineering

EXPERIMENT

29

DRYING—DETERMINATION

RATE OF DRYING

AIM

To perform the drying of the given sample.

To demonstrate the behavior of the drug during drying.

To determine the rate of drying.

REQUIREMENTS

Petri dish

Motar & Pestle

(1)

(1)

Glass rod

Hot air oven

(1)

(1)

Weighing balance

Beaker

(1)

(1)

CaCO3

PRINCIPLE

Drying is the process of removal of water or other moisture or other liquid from a substance with the aid of heat. In all the substances the moisture will be present in three forms; bound moisture, unbound moisture, free moisture. Absorption or desorption of moisture is continued till the equilibrium moisture content is reached. EMC is the amount water present in the solid which is in equilibrium with atmospheric moisture. Normal drying process is proceeded until the EMC is reached. Any attempt to remove moisture content below the EMC is the wastage of time and energy.

The rate of drying can be determined by performing a simple experiment with the help of a Petri dish and hot air oven. Prepared slurry in a Petri dish (previously weighed) is dried in a hot air oven and the weight lost with time is recorded. The water present in the slurry will be moved to the surface by capillary action as well as diffusion. At the time it reaches the surface of the slurry

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Preface_F

P.S.Sona Laxmi Publications PDF

A PRACTICAL MANUAL OF PHARMACEUTICAL ENGINEERING

Copyright © by Laxmi Publications (P) Ltd.

All rights reserved including those of translation into other languages. In accordance with the Copyright (Amendment) Act, 2012, no part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise. Any such act or scanning, uploading, and or electronic sharing of any part of this book without the permission of the publisher constitutes unlawful piracy and theft of the copyright holder’s intellectual property.

If you would like to use material from the book (other than for review purposes), prior written permission must be obtained from the publishers.

Printed and bound in India

Typeset at Shubham Composer

First Edition: 2015

UPE-9744-195-A PRAC MAN PHARMA ENGG-SON

ISBN 978-93-83828-43-2

Price: ` 195.00

Limits of Liability/Disclaimer of Warranty: The publisher and the author make no representation or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties. The advice, strategies, and activities contained herein may not be suitable for every situation. In performing activities adult supervision must be sought. Likewise, common sense and care are essential to the conduct of any and all activities, whether described in this book or otherwise. Neither the publisher nor the author shall be liable or assumes any responsibility for any injuries or damages arising herefrom. The fact that an organization or Website if referred to in this work as a citation and/or a potential source of further information does not mean that the author or the publisher endorses the information the organization or Website may provide or recommendations it may make. Further, readers must be aware that the Internet Websites listed in this work may have changed or disappeared between when this work was written and when it is read.

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Appdiex_IX

P.S.Sona Laxmi Publications PDF

216 A Practical Manual of Pharmaceutical Engineering

APPENDIX - IX

PHOTO COLORIMETER PRINCIPLE

Beer-Lamberts Law

The fraction of incident radiation absorbed is a function of the thickness (path length) and the concentration of absorbing molecules in its path. It can also be represented by the following equation:

A = abc

When the concentration (c) is expressed in moles/liter the expression becomes:

A=ebc

Where, e = The molar absorptivity c = The concentration (moles/liter) b = The length of the light path

Fig. 9.1:

Photo colorimeter.

Determination of amount of salicylic acid present in the sample by spectrophotometer

The sample solution is mixed with specific amount of Ferric chloride or ferric nitrate. The bluish purple complex formed between Fe3 + ion and salicylic acid allows its visual detection. Obviously, the intensity of the observed color is proportional to the complex concentration. Complex concentration can be determined by spectrophotometer.

Measuring the absorbance of the complex in the visible region (at 540 nm). The Beer�Lambert law states that the proportion of light absorbed by a solute in a transparent solvent is proportional to the number of absorbing molecules in the light path.

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Ch_49_F

P.S.Sona Laxmi Publications PDF

190 A Practical Manual of Pharmaceutical Engineering

EXPERIMENT

49

DETERMINATION OF RATE OF

CORROSION—TOTAL IMMERSION TEST

AIM

To determine the rate of corrosion of metal pieces in different solutions.

REQUIREMENTS

Metal pieces (Iron) diameter 20 mm and thickness of 3mm

(3)

Beaker

(3)

Round bottom flasks

(3)

Heating mantles

(3)

Glass rods

(3)

Reflux condensers

(3)

Weighing balance

(1)

Weighing Box

(1)

Concentrated solutions of acids

(1 M H2SO4, 1M HCl, 1M NaOH)

PRINCIPLE

Corrosion can be defined as the degradation of a material due to a reaction with its environment. In broad terms, the interaction between a material and its environment that results in a degradation of the physical, mechanical, or even esthetic properties of that material. More specifically, corrosion is usually associated with a change in the oxidation state of a metal, oxide, or semiconductor. Resistance to a corroding medium is often an important factor in the selection of material for construction of a chemical plant. Laboratory corrosion test are frequently the quickest and most satisfactory means of selection of most suitable materials for chemical plants. The

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