Determination of Ammonia in Household Cleaners An Instrumental Analysis Experiment Richard C. Graham' Science Research Laboratory, United States Military Academy, West Point, NY 10996 Steven DePew Department of Chemistry, United States Military Academy, West Point, NY 10996 Many different kinds of solutions contain ammonia. Some of the most common types of preparations are the household cleaners. Ammonia has been shown to be an effective erease cutter, and thus, the presence of ammonia is a desirabie addition to the formulation. Among the many different methods which have been used to determine ammonia is the Nesslerization t e c h n i q ~ eOne . ~ use of this technique is to determine the amount of ammonia which is produced by certain enzymatic reactions. A maior oroblem with this technioue is the potential interferencebf many of the alkyl amines. A second method which has been used to determine ammonia in soaos and detergents is the electrode method wherein a gas p& meahle membrane combination electrode is used." As with the Nesslerization technique, many of the alkyl amines interfere with the method. A third common method in use is ion exchange chromatography (such as with the DIONEX Ion Chromatograph) which actually determines the presence of ammonium ion. The disadvantages of each of these methods make it desirahle to explore alternative methods. A method, which has found application for determination of weak (pK. > 8) monoand ~olvorotic . .. acids. is to monitor the heat o~oduceddurine a neutralization r e a ~ t i o nThe . ~ equivalence point is noted by a sham break in the titration curve rather than inflection mint as with potentiometric monitoring of the titration. This procedure is easily modified to determine quantitatively such analytes as ammonia in solution. Experimental
Thermometric titratian data were obtained with a TRONAC model 450 adiabatic titration calorimeter. Temperature in the water bath surrounding the reaction vessel was maintained at 25.000 OC 0.0003 OC by a TRONAC model PTC temperature controller. Data were taken by titrating 50 mi of an ammonia solution (diluted with freshly
*
boiled deionized water to maintain the titration curve on scale) with a 0.4191 N solution of hydrochloric acid. The equivalence point was taken as the first sharp break which occurs in the titration run. See the figure for a typical titratian run. A total of four different household cleaners were examined. Results and Discussion T h e titration of the ammonia present was assumed to follow, for reasons of simplistic interpretation, eqns. (1) and
' Author to whom correspondence should be addressed.
"Standard Methods for the Examination of Water and Wastewater:' 14th Ed.. Rand. M. C.. Greenberg. A. E.. and Jaras, M. J., (Editors) American Public Health Association. Washington. D.C., 1976. "Analytical Methods Guide.'' 9th Ed., Orion Instrument Co., Cambridge, MA. 1978. See, for example. Hansen, L. D., Christensen. J. J.. and lzatt. R. M.. "Aoolications of Thermometric Titrimetrv to Analvtical Chemistrv." in "~ddernTltrlmetry-A Treatise." ~ordan:J. (,Ed&) Marcel ~ekker, New York. 1974.
Amrnonio Equivalence
t
Paint
'buret
off
E
+m
I volume of Titrant +
A
typical thermometric titration of an ammonia-containing household cleaner hydrochloric acid.
With
Summary of Household Cleaner Ammonia Content, Price, and Relative PricelMole Ratio Household Cleaner Bo Peep" Top Jobm
Parson'sm A i d
Normality1 Volume 946 ml
830ml 830 m~ 1038 ml
Price $0.34 $1.17 $0.36 $1.25
%a
2.0679/3.5% 0.6679/1.13% 2.001 13.4% 1.300 12.21%
Cost($)/ Mole 0.17 2.11 0.22 0.93
Obtained bv tibation of 50 ml of a dilvted howhold cleaner with HCI.
The table gives a summary of the household cleaners used, their respective prices, molarity, and relative pricelmole In this experiment, the student is asked to judge the best buy of the household cleaners based solely on the criterion of relative cost of ammonia present. The table gives a sample set of results obtained. In this particular student's experiment Bo Peep was iudged to he the most cost effective on the basis of ammonia Eontent only. The wide disparity of cost for the ammonia can he partially explained by the fact that many of the household cleaners in addition to the ammonia also contain surfactants or buffering agents such as sodium citrate or sodium carbonate. These additional components are evidenced in the titration as multiole slooes within the same titration (see fieure). As with any t;trati& where equilibrium is establishedYver; rapidly, each component of the solution reacts sequentially depending upon the relative magnitudes of the equilibrium constants. T h e enthalpy of protonation is, however, different for each component which is exhibited hy a differing slope since the slooe is orooortional to the enthalov of the reaction. The ammonia &tent of the solution is-determined from the Volume 60 Number 9
September 1983
765
portion of the titration curve having the same slope as the titration of a standard solution of reagent grade ammonium hydroxide of comparable concentration. The height of the curve is proportional to the concentration. Thus from the ti-
766
Journal of Chemical Education
tration curve, the identity and the amount of ammonia can be determined. No attempt was made to quantify or identify the surfactant portions of the cleaners.
