SECTION THREE 



I ounce (avoirdupois) = 28-3495 grammes. 

 I ounce (troy) = 31-1035 grammes. 



I pound (avoirdupois) = 453-5924 grammes. 



I I pounds = 5 kilogrammes. 



I ml. = o-ooi litre = i cc. = 16-23 minims. 



10 minims = 0-616 ml. 



I fluid drachm = 3-697 ml. 



I fluid ounce = 29-673 ml. 



8 fluid ounces = 236-583 ml. 



I pint (English Imperial) = 567-94 ml. 



I litre = 1,000 ml. = 33-81 fluid ounces. 



I gallon (English Imperial) = 4-5435 litres. 



I inch = 2-54 centimetres = 25-4 millimetres. 



I foot = 30-48 centimetres = 0-3048 metres. 



1 yard = 0-9144 metres. 



I metre = i -09361 yards = 39 inches (approximately). 



To convert Centigrade degrees to Fahrenheit, multiply by f then 

 add 32. 



To convert Fahrenheit to Centigrade degrees, deduct 32; then 

 multiply by f . 



DILUTION OF PERCENTAGE SOLUTIONS TO REQUIRED 

 LOWER CONCENTRATIONS 



It is often desirable to keep concentrated stock solutions of stains 

 and reagents and dilute these to lower percentages as and when required. 

 A simple rule, which may not be known to all readers for carrying 

 out such dilutions, is as follows: 



It is desired to prepare a dilute solution of X% from a more concen- 

 trated solution of Y%. 



This is done by taking X ml. of solution Y and making up the 

 volume to Y ml. 



Examples: 



1. To prepare a 0-25% solution of say, acid fuchsin from a 10% 

 solution of the dye. 



Here X = 0-25 and Y = 10. 



Therefore 0-25 ml. of the 10% solution is diluted to 10 ml. 



2. To prepare 100 ml. of o-^% solution of safranin in 70% alcohol 

 from a 5% aqueous solution of the dye. 



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