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From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Guide on various anti-freeze solutions for cooling systems, detailing mixtures and their properties.

Identifier  ExFiles\Box 151\3\  scan0017
Date  15th September 1914 guessed
  
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only necessary to add alcohol to the system, from time to time, to replace that which is used up.
Glycerine and water have also been used extensively for the reason that the boiling point of glycerine is about the same as that of water so very little is lost by evaporation. The use of glycerine is found objectionable however, because when enough is added to produce a low freezing point it rots the rubber hose connections and is so gelantinous that it does not circulate readily, especially is this true when it is used in a thermo-syphon system. The proportions of glycerine and water to use are indicated by the curve Fig. 2 or may be obtained from the table:

Freezing Point. Glycerine. Water.

+28 degrees Fahrenheit. 10 per cent. 90 per cent.
+15 do do 30 " " 70 " "
+ 5 do do 40 " " 60 " "
0 do do 48m " " 52 " "
- 5 do do 54 " " 46 " "
-10 do do 58 " " 42 " "

The difficulties in the way of using glycerine and water alone have led to the use of a mixture containing alcohol in addition. In this way a solution is obtained that has, in a large measure, the good points of both alcohol and glycerine. The presence of glycerine raises the boiling point, thereby reducing evaporation, yet the glycerine is sufficiently deluted to allow a free flow and to reduce its action on the hose connections to a negligible amount. The alcohol and glycerine are generally added in equal parts to the water, the amount depending upon the freezing point desired. Fig. 2 shows the percentage of mixture to add or this may be obtained from the accompanying table:

Freezing Point. Mixture. Water.

+20 degrees Fahrenheit. 15 per cent. 85 per cent.
+15 do do 20 " " 80 " "
+10 do do 24 " " 76 " "
+ 5 do do 27 " " 73 " "
0 do do 29 " " 71 " "
- 5 do do 30 " " 70 " "
-15 do do 32 " " 68 " "

Calcium Chloride in water is another solution that has been used with success. When purchasing calcium chloride it is very important to ask for the chemically pure salt as the commercial variety contains free acid which reacts on the metal parts of the cooling system.
  
  


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