Paraffin oil, when introduced into boilers, causes the deposit thrown down by the water to take the form of a soft mass of rounded particles, easily removable by the frequent use of the blowcock. It is evidently purely mechanical in its action, for the deposit shows on analysis a composition similar to that obtained by the evaporation of the water, whilst the oil can be detected and separated from the mass. The large amount of calcium carbonate shows how little change has taken place. In the table of analyses given under this section, it will be observed that in one case the proportion of iron oxide is very large, but this was traced to the employment of tallow along with the paraffin oil. After the animal fat had been stopped for some time, a new analysis gave the percentage of iron at a very much lower figure, and it has since gradually fallen to a normal amount. Paraffin oil soaks into scale which may have been previously formed in the boiler, causing it to split up and be easily removed. The difficulty as to the employment of this oil seems to be that its searching action is so great as to cause the thorough cleansing of the plates and consequent leakage at faulty joints. Its use is unattended by priming, and* the amount of the oil may be increased without fear from this source.

It is found necessary first to introduce the oil when the boiler is empty, but further supplies can be afterwards added without this precaution. The employment of condensed waters should be dispensed with where fatty oils are employed as lubricants, or paraffin may be substituted, and the use of the exhaust continued. Care must, however, be taken that the lubricating oil used be perfectly free from paraffin scale, otherwise the latter, finding its way into the cylinders, will form a hard cake very similar to that obtained when tallow is used. To the presence of paraffin scale may be attributed much of the feeling engineers have against paraffin lubricants. The heavier oils can readily be got free from the scale, and yet retain the viscosity so necessary for high-pressure engines, the lighter lubricating oils being perfectly suitable for low-pressure fittings. Several mixtures of paraffin oil with the fatty oils are to be obtained, but these have the same disadvantage as tallow, namely, the formation of a lime soap, which, however, is not so injurious in this case, from the presence of the paraffin oil.

The soda tar obtained during the purification of crude paraffin oil, and

consisting partly of caustic soda and partly of carbonate, with a proportion of the tar acids from the crude shale oil, furnishes one well-known anti-in-crustator. Its action is both chemical and mechanical, and the tar acids seem to have little deleterious action on the iron plates.

Table M. - Boiler Incrustations. - Paraffin Oil Employed

-

Well.

Well.

Well.

Ferric Oxide (Fe2O3)........

5.48

2.12

22.88

Aluminic Oxide(Al2O3)

Calcic Carbonate(CaCO3)

34.03

53.16

1.21

Magnesic Carbonate (MgCO3) ..

29.16

20.03

3.08

Calcic Sulphate (CaS04)......

4.04

10.52

50.88

Sodic Salts,etc..

0.26

056

0.36

Silica(SiO2)...

13.88

5.56

10.66

Organic Matter (including oil) ..

6.61

5.44

10.24

Moisture...

5.48

2.03

0.58

Total..................

98.94

99.92

99.89

Table N. - Boiler Incrustation. - Paraffin Soda-Liquor Employed

Town Snpply,

Bain Water, and Well.

Ferric Oxide (Fe203)..

2.12

Aluminic Oxide (A1203)..

Calcic Carbonate (CaCO2)..

84.86

Magnesic Carbonate (MgCO3)..

1.76

Calcic Sulphate (CaSO4)...

.. 3.52

Sodic Salts, etc.....

.. 1.37

Silica(SiO2)

3.02

Organic MAtter.....

..1.28

Moisture.....

..1.96

Total .. ..

99.97