44 INSTRUCTIONS FOR COLLECTORS 



in the form of a non-mineralized methylated spirit can be used as an alter- 

 native. Two types of methylated spirit are usually available — 



(a) mineralized and (b) non-mineralized. Only the non-mineralized is 

 suitable for preserving purposes. 



(a) Mineralized Methylated Spirit, which often contains a purple or red 

 dye and small quantities of pyridine, is a mixture of ethyl alcohol of a high 

 strength and crude methyl alcohol (wood naptha), with mineral oil added. 

 This is almost useless for preserving animals as it cannot be diluted with 

 water without forming a milky emulsion. 



(b) Industrial Methylated Spirit (I. M.S.), also called Ethanol Mixture, or 

 Rectified Spirit, is a non-mineralized methylated spirit containing 92-95% 

 alcohol by volume and about 5 parts of either crude or pure methyl alcohol. 

 This is sold by some retail chemists and all methylators for manufacturing 

 purposes. It is marked on containers as between 62 and 66 Over Proof. 

 There are restrictions in some countries which govern the sale of this grade of 

 spirit, and the collector may have to consult the Customs and Excise depart- 

 ment of the country concerned for permission to purchase, or the local 

 museum or hospital for information. 



Collectors need not assess the strength of the alcohol used with fine accuracy 

 but they should ensure that for long-term storage the percentage of alcohol 

 should never fall below 50%. 



Alcohol strength can be tested with an alcoholometer of the type calibrated 

 to measure the percentage of alcohol, or with a Sykes' alcoholometer which 

 shows the degrees above or below Proof. With the latter spirit should not 

 be used if the alcoholometer floats at under the Proof mark. British Proof 

 is about 50% alcohol by weight or 57% by volume. (Spirit must be over 

 Proof. I.M.S. is about 64 over Proof and contains 95 % alcohol.) For very 

 accurate readings the alcoholometer should be corrected from a table to 

 allow for the varying temperature above or below 60 °F (15-5°C); but for 

 temporary bird storage in the field, direct readings are close enough. 



Spirit can be diluted with water to a weaker grade, either by weight or by 

 volume. For dilution by volume of alcohol to a weaker grade for rough 

 field work, 95 % can be taken as 100% alcohol for these purposes and diluted 

 as follows. 



To make 80 % alcohol add 4 parts alcohol to 1 part water by volume. 

 70 V 1 3 



5 9 9 5 lyJ /O 9 9 9 9' 9 5 99 99-' 99 99 99 99 



10°/ 1 9 



99 99 1V /0 99 9 9 l 99 99 99^ 59 99 99 55 



For strengths other than 95 %, the following table can be used to estimate the 

 amount of water required to reduce 100 volumes of alcohol of a known 

 percentage by volume. 



Weaker grade 

 required 



ORIGINAL GRADE 



90 85 80 75' 



85% 



6.6 



— 



— 



— 



80% 



13.8 



6.8 



— 



— 



75% 



21.9 



14.5 



7.2 



— 



70% 



31.1 



23.1 



15.4 



7.6 



10% 



804.5 



753.7 



703.9 



652.2 



