Tallow is most usually employed, but the coarser and low class oils also occasionally find their way into the market. These substances cannot be too strongly condemned, as they are without doubt most hurtful. The oil or fat, at the temperature to which it is exposed, is partly split up into fatty acids, which act upon the sides of the boiler or on brass fittings, and partly combines with the lime present in the feed water, forming a lime soap, which, becoming attached to the plates, is burned, yielding a tough mass or scale, and causing very great loss of heat from its non-conductive power. The analyses given in Table K show the presence of a very large proportion of iron, and as neither water supply contained appreciable quantities, we are compelled to go to the boiler plates as the source. That tallow should continue in use seems extraordinary, as it is a well-known fact amongst practical engineers that any little good that maybe done by tallow on stray occasions, as on entering a muddy river from the sea, when a small quantity is said to be advisable, is far over-balanced by the damage sustained by the boiler plates.

The engineers of our largest railway companies and steamship lines unite in condemning the use of tallow in boilers; they even state that before a new locomotive or stationary boiler can be used without priming, steam must be raised in it several times, and the water afterwards blown out, so as to get rid of the oil used in boring the rivet holes, and that

soda may even be necessary before this can be accomplished.

Table K. - Boiler Incrustations - Tallow Employed

- -

Loch.

River.

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

11.60

25.72

Aluminic Oxide(Al2O3)

Calcic Carbonate (CaCO3)......

5 92

44.83

Magnesic Carbonate (MgCO3)

6.76

6.44

Calcic Sulphate (CaSO4)......

1.52

3.12

Sodic Salts etc...

trace

0.44

Silica (SiO2) .....

12.16

13.33

*Organic Matter ........

58.50

3.80

Moisture...........

3.64

2 24

Total ......

100.10

99.92

*Oily Matter ..........

57.47

3.20

Much controversy has of late arisen as to the presence of oily or fatty substances in "scales " and " feed waters." Macadam generally found considerable quantities in deposits derived from boilers where tallow was used, but it is most abundant on the inner surface of the crust and farthest from the fire.

No member of this series should be used in or about steam boilers, for even where employed as lubricants, they pass into the feed waters and cause much damage and annoyance. The analysis of a sediment from a condensed-steam tank, where tallow was used as a lubricant, illustrates the very large amount of oil which can find its way into feed waters from such sources: -

Table L. - Sediment From Condensed-Steam Tank. Tallow Used As A Lubricant

Ferric Oxide (Fe203) ..

50.21

Aluminic Oxide, etc. (A1203)

1.07

Calcic Carbonate (CaCO3)

0.31

Magnesic Carbonate (MgCO3)

1.28

Calcic Sulphate (CaS04)..

1.43

Cupric Oxide (CuO)

0.88

Sodic Salts, etc.....

0.11

Silica (SiO2) .., ., ..

1.38

♦Organic Matter

41.93

Moisture..............

0.87

Total....

100.47

*Oily Matter..............

41.36

The copper present was undoubtedly derived from the fittings, and along with the ferric oxide shows very well the action of the fatty acids on the metals.