98 



According to Wo. Ostwald (" A Handbook of Colloid Chemistry " 

 page 103), petroleum oil fractions of high boiling point are to be 

 classed as iso-coUoids, i.e., a category in which disperse phase and 

 dispersion means possess the same (or analogous) chemical composition. 



The ultra-microscopic examination of a number of mineral 

 lubricating oils (Dunstan and Thole, Jour. Inst. Petr. Tech., 1918, 

 4, 191) has demonstrated that optical heterogenity exists, although, 

 however, the degree of dispersion is exceedingly high. The same 

 behaviour obtains for the fatty oUs and it is possible that lubricating 

 power is in some way connected with this iso-coUoidal state. 



Lubricating greases ai'e examples of oil-water emulsions stabilised 

 by soap. Commonly sodium soaps are used for motor greases and 

 the proportions are lubricating oil (sp. gr. •900-' 910), 80 parts; 

 stearin acid, 15 parts ; and caustic soda, 2 parts. Part of the oil is 

 mixed with the stearin acid and this is added to the soda in 40 per cent 

 aqueous solution, with constant agitation. The remainder of the 

 oil is then incorporated. Cheaper greases are compounded with 

 Ume soaps. 



Acheson's oil-dag and aqua-dag are suspensoids of graphite in 

 oil or water containing a protective colloid (tannm). Aqua-dag is 

 made first, and the graphite is transferred from this to oil. The 

 oU-dag contains about 15 per cent, of " deflocculated grajjhite " and 

 is used in a dilute solution of lubricating oil (0-1 per cent, graphite) 

 with beneficial results to the bearings, which gradually become coated 

 mth a " graphitoid " layer. 



The colloidal graphite in oil-dag may be removed for analysis in 

 two ways. Freundlich {Chem. Zeit., 1916, 40, 358) throws out the 

 graphite by adding an electrolyte (acetic acid) to the benzol solution 

 of the oil-dag whilst Holde (Zeit. f. EleJdrochem, 1917, 23, 116) 

 adsorbs the graphite on recently ignited Fuller's earth in a Gooch 

 crucible. A German proprietary material named " Kollag " appears 

 to be similar to oil-dag. 



The influence of colloidal bituminous matter which is mechanically 

 carried over during distillation is frequently sufficient to prevent the 

 easy separation of paraifin wax from that fraction known as " heavy 

 oil and paraffin," and recourse is made to a sulphuric acid treatment 

 before refrigeration. The paraffin scale is usuallj^ discoloured and 

 contains a greater or less amount of uncrystaUisable material which is 

 removed by the process of " sweating," i.e., fractional fusion. This 

 operation serves to raise the melting point of the wax and also in part 

 to purify it. Final decolourisation is effected by filtering the melted 

 wax through Fuller's earth, bauxite, or prussiate charcoal. 



THE COLLOIDAL STATE OF MATTER IN ITS RELATION 

 TO THE ASPHALT INDUSTRY. 



By Clifford Richabdson, M.Am.Soc. C.E., F.C.S. {Consulting 



Engineer, New York). 



The presence of mineral matter in a high state of sub-division 

 in a system solid-liquid, the latter phase consisting of asphalt, reveals 

 some interesting phenomena, connected with the relation of surfaces 

 of solids and films of liquids, particularly where the mineral matter 

 is sufficiently subdivided to exist in a colloidal state as regards the 



