**Qestions and Answers**

**NOTE;—Readers are invited to send in questions, which will be answered in the order received. Names are omitted from questions unless otherwise specified**

**Poisonous Gases and Tank Discharge**

*To the Editor:*

I recently read in FIRE ENGINEERING an account of Cleveland Clinic Hospital fire wherein it was stated that _____itrogen dioxide was the cause of death of many of the persons who lost their lives at that disaster.

*Question 1.*** **Does celluloid when decomposing always give off nitrogen dioxide gas?

*Question 2.* Please give a list of poisonous gases that may arise in the event of a fire. Also explosive gases.

*Question 3.* Is my solution of the following problem, as given below, correct?

A tank of water 20 feet in diameter, and 20 feet high, is filled to the top. How long will it take to empty the same through a** **2 1/2-inch outlet wide open, communicating directly to a pipe which terminates four feet above the ground. The tank is set on uprights 60 feet above the ground.

The way I figure it out is as follows:

Height of top of water above outlet is 60 — 4 or 56 feet. Add to this the 20 foot depth of water and we get 76 feet as the height of the surface of the water above the outlet.

Back pressure created by this head is 76 x .434 or 32.984, or 33 pounds approximately. This is the pressure at the outlet, when the outlet is first opened.

Contents in cubic feet equals 20 x 20 x .78.54 x 20 or 6283.2 cubic feet. Multiply this figure by the number of gallons in a cubic foot, namely, 7.481, and we get the total contents as 47,000 gallons approximately.

The discharge from the 2 1/2-inch outlet is secured by the following means:

Discharge equals .80 x diameter x diameter x 30 x square root of pressure or .80 x 2.5 x 2.5 x 30 x 5.7.

This gives approximately 855 gallons per minute discharge.

Dividing the total contents of the tank, 47,000 by 855, we get approximately 55 minutes, the time required to empty the tank.

This answer would be correct, so far as I know, if the head remained constant, but every foot drop in the tank decreases the pressure at the outlet. This is the part of the question on which I would like definite information.

*Question 4.* Please give me a list of volatile liquids and their flash points.

*Question 5.* Please give me what information you can on this question: I understand how to find friction loss and change 3-inch hose to** **2 1/2-inch, but I have never seen any method whereby I can determine the friction loss on** **3-inch hose having** **2 1/2-inch couplings.

Respectfullv yours,

E. W. J.

*Answer 1.* Yes, when ordinary celluloid is decomposed nitrogen dioxide gas is always present. The quantity of the gas will, of course, depend upon the process of decomposition as well as the particular ingredients in the celluloid which is decomposed. Compositions of celluloid vary widely, and products of decomposition likewise vary considerably, depending upon the amount of air present.

*Answer 2.* It is presumed you have reference to any fire and not alone to celluloid fire. In such case, the gases thrown off depend upon the materials burning. It would be impossible to list all of the gases generated at fires of different types. This much may be said, however, that carbon dioxide is present at all fires and carbon monoxide at a great many.

*Answer 3.* Just as you suggest, an error creeps in where you consider head of water constant. A very fair approximation of accurate results would be secured by taking the average height of water in the tank, 10 feet. In other words, we would divide the 20 by 2 to get the average height and this figure, 10, would be added to the 56 feet to give us 66 feet instead of 76, as used in your calculation. Using this particular head, the results you would secure would be very close to 100% accurate. When the tank is full we have 20 feet to consider, whereas when it is empty we have no depth. Adding the 20 to 0, we get 20, which, divided by 2 for the average, gives us 10 feet depth.

*Answer 4.* You are referred to the “Condensed Chemical Dictionary,” published by the Chemical Catalog Company of New York, for this information. Space here would not permit listing all of the different types of inflammable volatiles and their flash points.

*Answer 5.* An approximate method which will your purpose in finding friction loss of 3-inch hose with 2 1/2-inch couplings is to find friction loss for a similar length of 3-inch hose with 3-inch couplings, and when you have secured this friction loss, add 10% to it. In other words, suppose the friction loss in a certain length of 3-inch hose were 40 pounds. To find the friction loss in the same length of hose with** **2 1/2-inch couplings we would add 10% of 40 or 4 pounds to the 40 pounds, giving us 44 pounds as the friction loss in the length of 3-inch hose with 2 1/2-inch couplings. This method gives you results which are slightly greater than you would secure by test with moderate flows in hose lines. Nevertheless, it is a method which plays safe.

**Sulphuric and Nitric Acids**

*To the Editor:*

Will you please answer the following question as soon as possible? Is nitric or sulphuric acid explosive or inflammable?

What effect have they on a person when liberated under fire?

What is the proper method to neutralize these acids when involved in fire?

Yours very truly,

J. S. M.

*Answer:* Nitric and sulphuric acid are neither explosive nor inflammable.

Both are highly corrosive; that is, produce a searing effect on the lining of the lungs, when inhaled. Nitric acid, in particular, is extremely hazardous from this standpoint, the fumes thereof frequently causing death when inhaled in sufficient quantity. Sulphuric acid, on the other hand, while not quite as deadly, presents a life hazard where it is encountered at a fire.

Nitric acid fumes are hard to detect when mixed with smoke, and hence are more dangerous than those from sulphuric acid.

Either nitric or sulphuric acid may be neutralized when present in small quantities by the use of soda, thrown directly in the acid.

When present in large quantities, about the only thing that can be done to reduce danger thereof is to drench with water.

Nitric and fuming sulphuric acids will ignite combustible materials with which they come in contact, but when diluted with water, this possibility is eliminated.

**Bode, Ia., Buys Apparatus**—The town of Bode and eighty farmers living within a radius of seven miles of the town have contributed to the purchase of fire apparatus.

**Two Pumpers Housed at Norristown, Pa.**—Two new pumpers have been officially placed in service at Norristown, Pa.