CHEMISTRY. 235 



TQ MAKE RAXCID OIL SWEET. 



A correspondent of the London Builder gives the following results of his 

 experiments upon rancid oil. 



The following substances will prevent oil from getting rancid: 



1. Sweet spirits of nitre. A few drops added to the oil. The effect is due 

 to the nitric acid of the spirit, oxidizing every thing but the oil itself. The 

 hydrogen has nothing to do with it. 



2. Creosote appears to answer even better than the last. 



3. Methylic alcohol (common "wood-spirit"), jf added in small quantity 

 to oil, will prevent its putrefaction, probably from the creosote, &c., it contains. 



4. Hypochlorite solution. The hypochlorite of soda is about the best, but 

 a little strong solution of chloride of Ihne does very well, shaken up with the 

 oil : when required for use, the oil may be decanted from the top, or draw* 

 off with a syphon ; or let the mixed oil and solution be poured upon a circular 

 filter, thoroughly wetted with water, and placed in a funnel, when the solution 

 will pass through the filter, the oil being left. Any liquid which does itot 

 perfectly mix may be separated in this manner ; the filter paper to be pre- 



viously wetted with the fluid intended to pass through. 



5. Small pieces of charcoal, soaked with diluted nitric acid, I have found 

 to possess similar properties to the above. 



Substances that will make rancid oil sweet : 



1. Sweet spirits of nitre. 



2. Creosote (very uncertain cannot be depended on). 



3. Methylic alcohol (very uncertain of little use). 



4. Hypochlorites (quite effectual in a few hours ; in a few minutes if boiled : 

 the dry salts are of little use). 



5. Peroxide of manganese (very good). 



6. Animal charcoal (very good, but takes a few days, unless boiled with 

 the oil). 



7. Charcoal (of no use unless boiled with the oil : that from beechwood is 

 best). 



IMPROVEMENTS IN THE MANUFACTURE jfSD PREPARATION OF 



OILS AXD FATS. 



Oil from the Avocado Pear Tree. The Avocado pear tree (Laurus Persea), 

 a native of the West Indies, produces a highly oleaginous fruit, which yields 

 an oil that promises to be useful in the arts. The Governor of Trinidad lately 

 forwarded some specimens of this oil to Prof. Hoffman, who states that the 

 oil has an acrid principle in it which he has been unable to separate, and also 

 contains much mucilage ; but that when treated with a small quantity of sul- 

 phuric acid, after the manner practised in France for the refinement of rape 

 oil, a very excellent oil for purposes of illumination was obtained, being, in 

 fact, nearly as good as sperm oil. The oil is also very suitable for the manu- 

 facture of soap, either in its unbleached state or after having been bleached 

 with chlorine. 



